@OP because there are just too many X's you do know you are on a bike forum correct? Would you go to the guitar forum and ask why do you have so many different guitars?

Bike are awesome but they all do different things. I wouldn't take my road bike mountain biking and vice versa. Plus bikes are awesome, having just one is boring and unless that is truly all you can afford and have space for more bikes the merrier.

Though I am at the point of thinning what I have just to stuff that really brings me the most joy and get more riding. However if I had the budget and the spacing I want I would probably add a bike or two but they would be full custom built titanium bikes with really nice parts on it