Why is it that...Please help me understand this...?

It drives me nuts, simply because as you said if you do have a question about an actual pregnancy, it gets buried under a flurry of "Am I pregnant?" questions. I think it reflects either a desire to be pregnant or fear or being pregnant on the asker's part. And yes I cannot stand it when people answer some desperately hopeful person ttc with "congrats, hun, you're pregnant!' because most of us know what its like to really really want a baby and I think its bad to help inflate someone's hopes even farther when only a pregnancy test can tell them the answer.