Different frequency ranges have different characteristics. Using Phone frequencies is like shouting really really loud. Other phones are shouting too, so you need to take turns shouting. But this does not really answer why you could not do it.
WiFi is a different frequency band that has a much shorter range than GSM, it also penetrates objects less. This is a good thing because it means that the number of networks that overlap is smaller. Of you were to use Mobile ranges then the systems would have a pretty long reach which would make you see quite many more personal stations. This would be a mess, since you would lose out on connection speed as you would need to share your space with more users. You are already seeing problems with WiFi in densely populated buildings with lots of home networks. Imagine multiplying that problem by including every station in a multi kilometer range. This can give you some idea why you would want to avoid using Mobile ranges.
I'm not really convinced Bluetooth is needed. However it is designed to be very very cheap so it's easy to add to quite many places. It is also pretty low powered so that is a plus.
A second reason is the phone frequencies are owned by the phone company, in some cases they paid thousands of millions of dollars for the ownership. In essence using this range is like trespassing in a factory. The owners will not look at this very favorably. Simply it is illegal, you can end up having a lengthy and costly talk with government officials if you mess up on this space too much. Since you are using a wavelength that has quite considerable range your unlicensed use will be heard for several kilometers, the phone company will know.
There is also a third reason. Innovation and developmental reasons. If we all converged to using one standard then there would be a much slower development cycle.
So in the end what you ask would be possible. Just not very practical, and more expensive for you as end user. It is also a question of how we have chosen to allocate resources, it may be that selling the ranges to private operators ultimately will be a bad thing.