You can take any sport and simplify it to make it sound dumb. However, sports, have been around for many thousands of years. So obviously, the human psyche finds them appealing even if they aren't the athletes themselves.
Football- 22 guys going back and forth on a field. Boring.
Baseball- A guy hits a ball and a group of other guys try to get it before he hits all bases.
Hockey- A group of guys going back and forth on ice.
Golf- Hitting a ball into a hole, how hard is that?
Bowling- It can't be that hard to knock over a bunch of pins.
Now these are clearly not my views, I don't even like watching professional racing TBH (Well okay, the professional NHRA dragsters are a lot of fun). At the same time I can understand why some people like it. Each car in NASCAR is more or less the same, so it becomes a competition of the drivers and pit-crews, and having a favorite driver is the same as having a favorite football team. When your favorite football team is down 3 points, are close to the goal line, and there is 3 seconds on the clock left in the game, does the coach tie it, or try for the win?
It's fun, it's harmless, and it's entertainment. To me, without these sports, including NASCAR, life would be incredibly dull.