How do you virtualize old hardware?
First of all, modern version of Vsphere only really support a limited number of old OS versions (with maybe the exception of Windows).
Take the case of FreeBSD. Only the most recent versions support VMware's vmx network interface. Previously, you needed the emulated intel NIC. But older versions of FreeBSD didn't even have a driver for that.
(Though, in the case of FreeBSD one could just install 10.1 and the compat5 package and just use all the old binaries - but how many people actually know that?)
Then, the p2v-tools don't support anything but Windows and Linux (with a couple of restrictions, like that you can't virtualize a Linux software-raid. Or couldn't last time we tried a couple of years ago).
And who wants to virtualize old software anyway?
Of course, there's also the customer.
We've recently tried to persuade a customer (who's really a department of a much larger customer with _very_ deep pockets) to virtualize his stack of DL380G5 servers (purchased in early 2008).
But due to some overlapping plans with his software-refreshment cycle for the 3rd-party app they're actually running, they've now renewed their lease of these old machines. But at least, I'm re-installing them with FreeBSD 10.1 (I think I previously upgraded them from 6 to 7 and now 8). And at least, they can run 64bit software.
And we've only got to make them last for two more years.
Then, there's the slew of customers with PHP5.3 apps (and some PHP 5.2 and some PHP 4, incredibly) where migrating the app to PHP5.5 would mean a complete rewrite (usually typo3-based websites with custom extensions). Because the customer often can't do the rewrite himself, he has to pay an agency. Obviously, the money for that is sort-of not coming forward. Sometimes, the customer is the web-agency, sometimes the actual customer.
A while ago, I migrated the data off a Solaris10 file and mysql-server to a FreeBSD10 system. That Solaris 10 box hat close to 2000 days uptime. 2000 days without patches.
But patches with Solaris were always a bit of a hit-and-miss and after Oracle bought Sun, you couldn't download them for free anymore anyway...
Software doesn't age, but hardware does.