SSDs are expensive when you're buying by the thousands and consider that, aside from boot times, they don't impact PC performance enough to justify the cost for MOST PCs.
It takes my work PC about ten minutes to get to a working desktop. Probably two minutes to actually boot to windows, three or four to get to the Windows logon (anyone who works Windows domains has learned that if you don't have some wait times built in, policies may not load and you get support calls), then another three to five after I log in for all the scripts, antivirus, citrix, and other crap to run before my desktop is fully functional.
Sure a MacBook Air can boot in under a minute. It also can't run most of what we use and costs WAY more than the average business computer.