I don’t know about others, but I can tell you the main reason why I like it.
I’ve had to work with not one, but two guys who were exactly like Sheldon Cooper from the show, in terms of intelligence and character. They also quite looked like him. That was in different cities and different jobs. Both were absolutely self-righteous and 100% full of themselves. One of them seemed to think of himself as second only to God himself. It was brutal.
So, watching the series provided me with a lot of comic relief.