There may not be any "free messaging" or similar offers is my guess. In fact using ECH it is already possible to spoof the SNI but make a real TLS handshake to the underlying domain; you can try it on my test website[0] with wireshark open on the side (if your browser supports ECH)
I find it pathetic that vendors and ISPs are snooping SNI headers to block things, looking at you, UK.
Also, I wonder what will happen if those instant messaging apps move to Encrypted SNI (ECH), will they just not work, or is there fallback?