Some people have kids, some move and can't take their tanks with, some have a crash and don't want to keep doing it. I recently came back after a 7 year break, but when I got out I had been working at a public aquarium for 6 years, was working fish store retail on and off (maintaining the entire department), and running a maintenance business myself on and off. Needless to say, I was burned the f*%& out with fish and needed a break. Best thing I ever did, in all honesty.