I did not read the other replies so forgive me if this was already said.

COMPETITION!

It gets you with other people interested in the same thing. I used to race nitro touring with a club in Okinawa Japan. It was the best time I ever had with R/C cars. When I was reassigned stateside, no one raced touring cars. I was bored and quit them. I picked up airplanes and joined a local club and back in full swing dropping cash like it was on fire.