RHEL7/CentOS 7 is one of the more significant distributions out there, you can yum install version 1.12 of nginx. It wasn't until 1.13 shipped that nginx picked up any support for http/2.
On the Apache front, mod_http2 didn't ship until 2.4.17, again CentOS 7 and other RHEL7 based distributions lags behind on 2.4.6.
Sure, that doesn't mean you couldn't compile / install your own version, but for a lot of people that's just not likely to happen. Sticking with the distribution version keeps you within any support contracts, gets you security patches etc. and all the information you need to keep auditors and the like happy.
