why is there no initiative to get Linux mobile up to speed?
There is. It just lacks a corporate sponsor, so it is going slowly.
Edit: It is also slowed because there is very little fully open source phone hardware, today - and of what there is, very little of it is pocket sized. This means phone OS maintainers have to rely on various hardware vendors cooperating, which is rare.
Also, the owners of the phone towers also probably don't imagine much benefit of having fully independent devices join the networks they maintain. I don't know how much help is needed from phone tower owner conglomerates, but I imagine we don't see enthusiastic support there, either.