No I have never really understood it, and I am not convinced that the officials do either.
Agreed, life was much simpler before they messed up the rule. As Danny Blanchflower once said " if he's not interfering with play, then what is he doing on the pitch".
For younger posters, Danny Blanchflower was a great old wing half (midfielder) in the 1950's/1960's. He was also quite outspoken and controversial for his time and famously refused to appear on This is Your Life. He also was one of the first pro footballers to appear on the adverts for Shredded Wheat his punch line being " pass the hot milk please".
I'm rambling, I'll get me coat and the zimmer frame