I talked to someone who had to re-ip his home network because he was using a subnet of 10./8 that conflicted with his VPN/work access. It's still possible to conflict with a local network you're on, it's not that nobody ever uses a 172.16/12 block.
A company I worked for, which is basically a group of a dozen acquisitions, uses practically every RFC1918 block which makes things really annoying. 10./8 used by IT, 192.168/16 used by company X acquired in 2004, 172.17/16 used by company Y acquired in 2011. The list of routes the VPN software installed was impressive.
I think if I were VPNing from a campus or an office, things would be different. Hotels, coffee shops, and corporate guest networks all seem to either like 10/8 or 192.168/16.
By the way, I use 172.30/16 for my home net. I have personally seen use of 172.16/16 and 172.31/16 before.
A company I worked for, which is basically a group of a dozen acquisitions, uses practically every RFC1918 block which makes things really annoying. 10./8 used by IT, 192.168/16 used by company X acquired in 2004, 172.17/16 used by company Y acquired in 2011. The list of routes the VPN software installed was impressive.