Because, and I really mean no offense to them, their phones fucking suck. Like, dogshit slow hardware with terrible drivers and a modem that barely works with last gen tech.

Their most advanced phone is based on a >10 year old SoC, that wasn't even that good when it was first released.

And even then they still don't live up to their promises, it is still not open hardware - there are a bunch of proprietary firmware, but especially silicon on these devices.