They're not meant as wallets - they're meant as a hot / short term balance for using the site.
If someone keeps his life savings on a social media buffer ... It's his own fault
Completely agree from a user standpoint, sure apps can have support for connecting to your LNDhub or something like that if you never want to trust anyone.
I think the big thing is either companies rug users or governments can capture company to rug users, but like you say its minimized by not having a large amount of sats on any one service