Because you often have to set the damned thing up using IPMI or other such things to get them remotable *before* you can get remote access even working. Other times you want to work on a file that lives on the system without dragging the file off the system or finding some way to get access to the local file storage on that system from your remote station.
In a unix world the shell is all. I just need one port open and I can get through to do my administration. No additional services, no additional windows, no nothing. Just one black box per server. In the Windows world I have to strip the bloody server naked and let all the bits hang out so that I can even edit a text file! WHAT. THE. FUCK.
Microsoft still lives and breathes eggshell security. Harden your edge, but behind that edge you need to wander around with your WMI, SMB and $deity only knows what else hanging out just to do basic administration! This is in contrast to a Linux world; there I have a hardened edge and layers of security - from obscurity by changing SSH off default ports to things like Fail2Ban to lock out attacks to layers of logwatching - that lock down a server INSIDE my network just as though it were facing the internet itself with no deprecation in usability or administerability.
Look, I don't buy eggshell security. Securing the edge is not enough. A) the edge is coming to you. IPv6 will eat your family. B) Something behind your edge is always compromised. Wee willy wonka the lobotomised salesdrone really likes barney BDSM porn and he's perpetual infected. Meanwhile, you forgot to firmware update your IPv6 lightbulbs and half of them are supporting malware that's probing your infrastructure from the inside.
So no, I don't want to use the PowserShell ISE. This doesn't solve my problem of opening a test file on the remote server without opening more holes. Not only that, the damned thing is Windows only; I stopped using Windows as my primary desktop environment ages ago. Have you seen Windows 8? Microsoft lost the plot and their corporate ego won't let them regain it.
Powershell is a necessary evil. It is unquestionably the future of administering Windows Servers because Microsoft says it is the future of administering Windows servers. What it isn't is good enough. It's all sorts of bitchin' and powerful but it is still designed solely for cleanroom sysadmins with their procedure manuals and testlabs and 3 month concept-to-implementation timeframes.
It is not something that lets me log in to a system and fix the fucking thing. It is a configuration tool that I see akin to "the Cisco IOS for Windows Server and associated applications." You don't log on to a CIsco router and just fix it. You never make live changed to a production unit without simulating and testing and layers of covering your own ass.
PowerShell is the same thing. You build your PowerShell config carefully in your cleanroom and then you push it out to the system and set that system's state. PowerShell really, really wants to be Puppet when it grows up. Given the awesomeness of Puppet, DevOps as a model for enterprise and commercial midmarket IT and so forth...that's great! Go Microsoft!
Systems administrators for smaller shops where budgets, staff and every other conceivable resource are as minimal as possible are firefighters. When you fight fires all day long, you want this. This is what Bash and the associated bog-standard utilities are.
When I'm in the middle of trying to put out 50 fires at the same time and you tell me to use PowerShell you are telling me to put out a burning building with this.
PowerShell is not a way to administer a system. It is a way to configure it. They are still completely different things. You can get yup on your horse and sneer disdainfully at the rest of the world and say asinine things like "well, if those sysadmins were any good, they'd never have fires to put out because they'd have adopted DevOps and be doing everything with huge pre-planning and simulation and testing." I'm sure you've thought it more than once reading this comment.
The reality of the matter, however, is that the majority of systems administrators simply don't get that option. They aren't in control of the budget. They don't set corporate IT policy. They don't have much control over any aspect of their jobs, really, and they simply do as they are told or they get replaced. They are told what to do not by some senior IT person who is themselves responsible for setting policy, but by the accountant, the sales clerk, the marketing wonk, the CEO and the janitor.
In most companies, sysadmins are the lowest ranking member of the corporate structure. They are there to serve. To make things happen whenever they are told and they are not expected - or allowed - to talk back. If they say no, they get fired; pure and simple.
In this situation, these people are fighting fires all day. They are fighting fires because they have to make quick changes to live hardware without simulations or a testlab. They need to back all this up (before and after) and they need to manage hundreds (if not thousands) of different types of devices and applications.
They move from device to device, server to server, application to application solving other people's problems in real time. This is why they can't use eggshell security. IT could be months or even years before they get back to a given system and then only because it did something it wasn't supposed to.
Every system they use has to have a complete set of tools on it. They can't wander around remotely accessing the system from their carefully maintained desktop; there may be layers of firewalls, VPNs, and gods only know what else between them and the target system. They may be RDPing in to server then RDPIng into another system then launching PuTTY to manage something because of a series of political and economic decisions taken by the business over the course of decades that isolated that system in that office in this particular way.
PowerShell as it stands today is virtually useless in that environment. Again: it is for configuration not administration. Maybe next version...