If you have an Android or Apple phone, there is likely a whole collection of backdoors to any taste (no, every eye looking at the sources won't notice a backdoor ; people are not stupid, backdoors are not obvious ; and also your phone's firmware is a binary you've downloaded from their update servers, you haven't seen the source it has been built from) allowing special services to install spyware to it. Maybe not from Google or Apple themselves (which I wouldn't trust either), but below the chain (no, you don't necessarily need sources for that), does that really matter? The difference with desktops is that people tend to make choices about security there, bigger chance of failure.

I mean, there should be a reason governments are fine with popular and easy E2EE when it requires to login on such to use it even on desktop. Like WhatsApp, Signal and what not. That is, we don't see them sabotaging, killing, prosecuting, forbidding or otherwise preventing the other kind, but we also don't see black holes in astrophysics. It doesn't mean we can't say with high certainty this happens.

An analogy. Humans prefer to eat behind a table from dedicated dishes using dedicated cutlery. Despite them being able to eat on foot and that being available in more places. Just like that humans would prefer to text others when they don't have other distractions and with a faster and healthier (for your hands) input device, like a normal keyboard. If most people don't do that, there must be pressure. If we can't determine its nature, it's likely masqueraded. If it's masqueraded, then it's a power interest.

TLDR smartphones are a conspiracy. Conspiracy theories are usually bad because people assume conspiracy before more probable reasons. Not the case here. A few supercorps and their pyramid-shaped ecosystem allowing spying on levels unprecedented in history are very likely to have conspiracies.

Also yes, I've lost my mind, but in this comment the part indicative of that is that it consumed time to type in order to exist where nobody cares and not its content.