I know very little about antenna technology, but physics might play a role. 2m/70cm is pretty far away from the few-cm-wavelengths of somewhat modern cellphones (70cm a bit less so). For FM radio, the common workaround was to use the cable of plugged in wired earphones as antenna, but I don't know how well that would work for bands where the transmitters aren't as unbelievably strong as they are for FM radio.
And then there's of course the fact that almost nobody is asking for that, so the engineering and maintenance effort behind it would be insane in comparison.
And then there's of course the fact that almost nobody is asking for that, so the engineering and maintenance effort behind it would be insane in comparison.