Motivation is simple: sometimes you are interested about driver ahead/behind in standings during the race ( "What's the guy ahead last lap"), but other time you see car in front of you on the track and you want to know, who is that (might be lapper, right? Than you need to figure out his position, now in iRacing you see e.g. position 22, but somebody crashed already in front of him, so CC sees him already as 21... really difficult to know what P#N you should ask).
So there should be some other wording like "driver" when you ask for standings related person and e.g. "car" asking for immediate car in front/behind of you on the track.