Bike porn

Cool. So you're just not into the whole thing. Which is fine.
But it is definitely not Takeshi's Castle on wheels. It's a Sporting event as you've mentioned.
A quite important and serious one, within Japanese culture/society, since it's the only legal way of betting.
NJS is they're bureau of control over every single component used on track racing. That's it.
Westerners made it what it is. A fucken circus.
Japanese are Japanese, Their Keirin is merely a reflection of the whole lot.
IMHO that's what makes it great.

I went to Keirin once, would have been about 2002.

It cost 50p to get in, including a bus from the train station. The bus was full of middle aged men in cheap suits who stank of whisky, despite it being midday. The stadium stank of fags even outdoors and everyone looked sad and depressed. The races are good, but over in a few seconds and there is a long wait before the next one so everyone can go and bet. It is definitely not the only place you can bet in Japan (horse racing?).

It is about as depressing as passing a hospital and seeing a man outside in a wheelchair attached to a drip swigging on a can of beer and smoking a Lambert and Butler.