It's hardly a surprise. It takes time for people to migrate to new protocols. Not everyone can just leave 20 years of engineering effort behind and switch to HTTP2 because it's a bit faster in some situations.
HTTP2 has multiple optimisations e.g. I only just realised it compresses XMLHTTPRequest requests, not just responses.
We use CloudFlare, so most of our users get HTTP2 even though our own infrastructure is still HTTP1.1 (however some corporate customers have proxies, which usually downgrade the browser connection to HTTP1.1).
We log whether HTTP2 or HTTP1.1 is used by the browser by JavaScript reading `window.performance.getEntries()[0].nextHopProtocol` which is supported by most modern browsers.
We use CloudFlare, so most of our users get HTTP2 even though our own infrastructure is still HTTP1.1 (however some corporate customers have proxies, which usually downgrade the browser connection to HTTP1.1).
We log whether HTTP2 or HTTP1.1 is used by the browser by JavaScript reading `window.performance.getEntries()[0].nextHopProtocol` which is supported by most modern browsers.