I guess we have to choose our poison. If the chat is RCS on both ends then it's Google or Apple reading the text. I don't buy any of the E2EE marketing. Some time force your phone onto LTE over Wifi and watch who it is talking to. Even with RCS every keypress
on Android at least goes to the wireless provider over a VPN tunnel for spell check. I found it still does this even if I disable spell check, just less. If it's plain text messaging then it's still plain text over SS7 and the wireless provider can see it in their messaging gateways. I just assume any messaging sent over a phone insecure.
I'm sure, in the general sense, this information isn't used for evil.
Maybe. I do know there have been cases of people bribing lower tier support in wireless providers to do SIM swapping. I don't know how often this occurs or how often they get caught. Things are logged but someone would have to know to look at the logs. I've also heard that employee churn is high in support so they might be long gone by the time anyone looks.