Actually Windows 7 is currently less than 25% of the marketshare and a lot of those are in companies running dedicated software that controls equipment. Browser stats are showing it really shrinking as an OS for cruising the net. That is good as at this point it has not had security updates for nearly 11 months as it is fully NOT SUPPORTED anymore. So I can't image why you would need it fore security reasons, but I know lots niche reasons to stay on an old system exist.
These are current usage stats: