You'd think so, but it's not even close to true.
For example Macs and RedHat systems require HDCP if you've used Spotify or Apple Music since the last reboot (which applies to most speakers).
Some Chromebooks can't provide direct display out but cast to a ChromeCast instead, which also always requires HDCP.
We've also had talks on media and cultural studies which use a clip from e.g. a Netflix or Amazon Prime show as part of their talk. HDCP is almost guaranteed in this case.
If your HDMI chain signals that it can't handle HDCP, some computers will obey that (and downgrade or stop playback). But most broadcast HDMI tech can't even signal that HDCP is unavailable, so you'll get HDCP by default.
That's why every major venue, university or event has HDCP killers stockpiled. For 1080p60 that used to be cheap chinese HDMI splitters, nowadays it's mostly these Hagibis cards. If they're really fancy they'll have an HD Fury with HDCP removal license, but those cost ~$600.
