Are you asking why we like quads vs. other multirotors, or just in general? For me, I prefer quads over other multirotors because they're a good balance of simplicity and cost vs. stability. Tricopters are nice, but they're going to hold a bit less payload (FPV gear, etc.) for a similar sized build and you have to deal with servos / moving frame parts. Other multirotors are great too (more than four rotors), but then you get into increased investment since everything costs more - frames, more motors, more ESC's, bigger batteries, etc.
The only thing I don't like about quadcopters is when I have to watch hundreds to over a thousand dollars of my money crashing into the dirt when it happens! And I guess also there's the fact that for the most part, I have to get in the car and find a good field to fly in, as opposed to RC land vehicles, where it's safe to enjoy them right outside my door.