Why does Russian aircraft that isn't SU-34 cannot carry more than 2 R27ET?

Question in the title, but it really bugs me that this limitation exist. i get limiting R27ER because of MTOW issue but in stronger airframe that can carry multiple ER, why not do the same with ET?

I think the other rails are not wired for them.

At least that is what i have heard.

Maybe i was expecting something else like “doctrine is to put as little IR missile as possible” or something to that effect but tht sounds kinda disappointing lol.