Because space is really, really unhospitable. We haven't colonized the surface of the sea, the top of montains, nor the glaciers of the Antarctic or Greenland, yet all of them are much more suited to human life than space (and as such, humans have occasionally been there for ages).
Living on Mars is pretty close living on the top of mount Everest, if mount Everest was in the middle of the Pacific and all you have to go there are sailboats that take months. It's not a place to settle. And deep space is even worse!
There will likely be people working away from Earth's orbit in the next decades (like we have people working in boats in the middle of Pacific), before being eventually replaced by autonomous machines. But the idea of space colonization is pure fantasy that doesn't hold any water.
Living on Mars is pretty close living on the top of mount Everest, if mount Everest was in the middle of the Pacific and all you have to go there are sailboats that take months. It's not a place to settle. And deep space is even worse!
There will likely be people working away from Earth's orbit in the next decades (like we have people working in boats in the middle of Pacific), before being eventually replaced by autonomous machines. But the idea of space colonization is pure fantasy that doesn't hold any water.