The caniuse.com data on http/2 appears to have some flaws.
Biggest buckets for browsers that support SPDY but not HTTP/2 for our website right now are:
a) Chrome for mobile
b) Safari on older Mac OS X versions
c) Older Chrome for desktop versions
d) Internet Explorer (small impact)
Other websites might see different ratios depending on their audience.
Stay tuned for instructions on how to gain protocol version insight for your own website on CF.
A awful lot of companies still use IE and not Windows 10 ;)