Sheriff pulled me over and let me go?

I got pulled over by a sheriff a little after midnight. He was from a different city than the one we were in. My eyes were bloodshot and I knew I smelled strongly of marijuana, because I had just came from smoking. I was shaking and he asked me if I had known why he had stopped me and I replied," No". He told me I caught his attention when I blew my horn at a driver who cut off in front of me and also my right running light was out. He then asked for my license and registration, then proceeded to go run my ID to make sure I, "didn't have any warrants." A few minutes later he let me go, saying he wouldn't write me a citation for my taillight, but to just make sure I get it fixed. Any reason he decided not to search my car? I thought it was because I was 17 year old minor, and it would be too much of a hassle to arrest me, tow my car, take me to jail and call my parents to come pick me up. Or could it have been the fact that he was a sheriff of a different city than the one we were in. What could have made him just let me go and not search my car?