Carriers Are Overpowered

I'm not asking for carriers to be nerfed (I play protoss and I'm self-serving) I just want to know why more people don't use them. It seems like only whitera and I realize their awesomeness.

By OP I'm only referring to pvz and when combined with psi storm and archons, but when I say OP I mean completely and utterly broken.

I just played a pvz in which I spent pretty much the entire game on somewhere between 0 and 2 mining bases while my opponent took 6 bases. I managed to turtle up for 40 minutes, however, and then attacked with 5 ht, a couple archons, and 12 carriers. My opponent built 5-6 remaxes worth of hydras and corrupters, and dodged my storms not too badly, and still didn't even touch my army.

I checked the replay and saw that before I moved out even, when I had engaged with far fewer carriers, he lost twice as much as me. Then when I attacked I lost *gasp* 2k worth of resources while he lost 30k+.

The only problem with carriers that I can see is that getting to them without dying is difficult.

Has anybody else experienced the invulnerability of mass carrier/storm? Why do I never see anybody else use them?

PS: does this go here or in general starcraft? I'm not sure