Allowing long range use would increase possibility of interference this it would require users education on radio operation which means introducing licencing. That would limit access to the band for those who do not need or are unable to learn advanced technical stuff. Amateur radio is long range alternative for advanced users.

Short range of PMR at 446 MHz is intentional. It would be wrong to allow long range,that would mean higher possibility for interference. PMR is band dedicated to free use of everyone without requirement of any knowledge or license. Most of the PMR user do not even know much about radio and especialy interference and how to not cause it or avoid it. So, short range solves issue by minimising possibility of interference.