I will be blunt.
It's because none of the video chat apps are competing on features, only on user lockdown. Their KPIs is how many users they have, and that only needs enough features/price to convince the corporate buyer which rarely accepts feedback from larger set of employees.
As such, outside of certain older very expensive corporate videoconferencing setups that remember targeting inter-corporate meetings and the like, the actual feature set ossified. You get some things that are easy to demo in 1:1 call, you get locked down room systems that leave me weeping for Webex ffs, and you get omnipresent WebRTC in-browser setup that often murders your CPU unless you get lucky.
I find it really bad that the best video conference experience I ever had involved Cisco Webex hardware and Bluejeans, all interconnected with so-maligned SIP. And before that, the glorious days of wider ITU-T based video conferencing, like NetMeeting with its whiteboards and active screensharing.
Imagine if video conferencing solutions competed on top of common protocols, and you'd separately invest in infrastructure and clients? Instead of the rare enterprise cases where Lync/Teams/Webex/other SIP is set on dedicated lines in large corporation, make similar setups common everywhere (WebRTC/SIP bridges/transcoders on the edge, with dedicated bandwidth bough by company, etc.?) with vendors competing on something more than "you have to use our stack because we don't interoperate with anyone else".
Sincerely, someone who has had enough keeping 3-5 video conferencing apps around.