They don't. Perhaps all devs get more than one machine, but not every employee ("blue badge") gets a 2nd or more system. My sole company-issued computer is a ThinkPad.
Afaik 2 machines are almost mandatory
1. Dev machine
2. Email machine
The 2 biggest orgs inside MS are Office and Windows, devs in both of them can't have a single machine doing both the above tasks. (And VMs suck for disk based I/O, and that becomes a factor when you have multi-hour build time)
Yes, economy does impact internally at Microsoft. Thankfully, we have Hyper-V to have more than one OS in a given box. But back in the old days, two machines per person was pretty standard. I no longer work for MSFT, so not all orgs still stick to the same policy
That's really odd. I used to work under Windows Live org, and all the Ops we know have more than one machine (at minimum, a laptop and a desktop). Even the orange badge has more than one machine...
Honestly, the only blue badge that doesn't really need more than one machine is PM. Both SDE and SDET definitely need more than one to develop and test. Ops can manage a cloud with just one, but in theory, we all know that Ops has access to a ton of VMs, so I consider them as more than one machine.