@cynicalsecurity I suspect some law enforcement agency, grounded in the old school telephone recording want to do the same on modern communications (which is quite idiotic for plenty of reasons).
In the meantime, yes they do end-point compromise, but that's a much higher barrier than just sending a request to a carrier. (Finding and weaponising vulnerable is expensive, and you may need to compartmentalise vulnerable usage not to risk compromising important ops by the implant getting noticed in an unrelated ops).
Imho, end point compromise higher barriers to widespread deployment is an important feature.