If there so many planets out there in space why aren't there any human colonies on other planets?

There may be, or at least creatures similar to us - not as colonies in the settler sense, but native to their planets.

However, we cannot know this; and we have no foreseeable way to colonise them.

Even our nearest planet theoretically viable for human visits - Mars - would be a very unpleasant destination no-one would want to "colonise".