Why very less people play KIA if it is that popular?


I know at least a friend or two who plays it, but I don't think KIA is super popular. It is usually very "strategic" as you say (or at least takes knowledge of positional ideas), so I think this discourages many beginners from playing it.
By far the most popular first moves are 1. e4 and 1. d4 among beginners and strong players alike. I will note though, KIA is not the same as 1. Nf3 (Reti) because that is only the first move. KIA can arise from transposition from 1. Nf3, 1. c4, 1. d4, 1. e4 and many other moves.
I think the KIA is a solid opening, but I don't see many players playing it regularly either.