[Beltalowda]

Maybe; I don't know. Telegram has the same incentives (and I believe they have some crypto wazamabob as well). I think it's much more likely that it's just easier for them: abuse is a serious issue and the more "closed" a platform is, the harder (not impossible, just harder) it becomes to abuse it (see: email). And not having to worry about third party integration/APIs, compatibility, documentation, etc. also makes their lives just easier.

Getting all of this to work well with E2E requires extra thought (how do you make messages available on two devices?); Telegram hasn't nailed that either. I don't especially care about this, but a lot of people do.

Essentially, there are basically no practical upshots for them, and it's just more effort.