Virtualisation is no silver bullet. I probably virtualise about 95%, but there's always a fringe case.
Good example is wanting to have HA for a service rather than just for a VM. In which case you'll need application level HA. Application level HA takes the wind out of virtualising somewhat, as you'll likely gain no benefit from the VM being HA (as you'll have multiple VM's running the service), and also likely that each VM will have it's own copy of the data - meaning you're taking up a sh!t tonne of space on your very expensive SAN.
Using Exchange as an example;
Lets say you use Exchange for the application level HA via a DAG. This is great, but means we're getting very little benefit in terms of HA by running as a VM. I've got two Exchange servers running on separate VM hosts, but regardless if the VM crashes or one of the hosts dies, Exchange keeps running... Exactly the same as if I had two physical Exchange servers rather than virtual.
Now running our imaginary Exchange servers as VM's, we're now making things expensive, as each Exchange VM has it's own copy of the mailbox databases - so that's twice the data I'm storing on the expensive shared storage SAN.
Things like Exchange can eat up your storage, to the point where you may need 10TB for each Exchange server, yet your SAN is only 30TB in total. So that's 2/3rd of your SAN used up straight away, and the cost per TB isn't usually that great with the typical SAN.
All of a sudden, you take a step back and realise that it would be considerably CHEAPER, and you get the same levels of resilience if you just buy 2 x DL380's or 730xd's and use local cheap storage instead.
You then have a load of extra capacity on your virtual hosts, plus your SAN has oodles of space left on too, saving your a fortune as you don't need to ask the FD for another £20k for a new shelf on your SAN that you brought only 6 months ago.
One big benefit that the article didn't touch one was how much easier virtualisation can make backup and DR. Agentless backup solutions (like Veeam, others are available) just rock my world - if it's on the virtual cluster it's getting backed up. No agents, no tapes, super fast restores.
After providing hardware HA for a server, it's the portability, manageability and backups that make virtualisation a default choice personally - but still it's not for everything, everytime.
P.S On a side note, who the hell is working in IT in 2017 and doesn't know where to start / hasn't used any virtualisation? Seriously?!