I know it's just meant to be cute and funny (and it is!), but it works quite well with the whole theme of Kakeru gradually becoming more and more feminine. Preteen girls tend to do things like this because they like the attention, without any clue as to why it works.
It reminds me a bit of Nono from Stella no Mahou not understanding why pictures she posted online showing her thighs got more likes than the others did.