Well, the reason why not is because you selected colonize only home type at the start of the game.
It's a hard code thing that cannot be gotten around once you select it at game start.
As Dogscoff said, the only way to colonize these worlds is to allow them to be colonized by someone else, and then trade for them, or take them.
If you want to be able to colonize the other types yourself, you will have to change the game settings at startup and not select that option.
It was put in as an option to slow down games, and it does a pretty good job of it
Geoschmo