Rockford

Can anyone tell me why I spent all day yesterday with the theme from the Rockford Files stuck in my head? I was humming in the shower first thing and realised it was the Rockford Files; thereafter it was in my head all day long. I haven't seen it repeated anywhere recently or seen any old film on TV with James Garner, so gods know why it suddenly leapt out of the murky depths of my brain (I don't care to look down into the recesses too much, I'm not sure what I'd find in there).