A lot of sites are like this but they miss the point... which is that I don't want to give them my mobile phone number in the first place. I might, if I could

A lot of sites are like this but they miss the point... which is that I don't want to give them my mobile phone number in the first place. I might, if I could reasonably trust that they really do delete it, but I think experience shows that we can't completely trust most companies nowadays.