Well the 3DS is primarily meant for children so the chibi aesthetic makes sense there the most.
If it was due hardware limitations games like Monster Hunter, resident evil revelations, MGS3 or even Kid icarus Uprising wouldn't exist on the 3DS.
Well, you kinda mentioned four titles there. I am not saying non-chibi is physically impossible on 240p, I'm saying aesthetic is a decision in which things like resolution ARE FACTORED in, among others.
Which they clearly are if you ever read stories from (famous) game designers, including miyamoto's super mario design. Chibi is usually associated with low texture detail and has simplified, more rotund/less narrow body shapes, which is something that helps recognition when your resolution is very poor (rendering thin strands of hair and limbs resulting in a blurry mess of pixels). It's why MH looks horrendous on the 3DS/PSP compared to emulator, whereas you can compare a game like wind waker or dragon quest 8 (this one not because of a chibi artstyle but its use of "anime-like" simplified textures) inherently suffering much less from that issue.
You could also compare the slight difference in style with the rune factory titles between Wii and (3)DS. I'm certain both of those systems/games are targeted towards the same exact crowd yet their character designs were still changed. Probably because it just fit better with each hardware, or so they felt.
Same goes for spriting. Try asking any good sprite artist if they're better off going chibi or 'realistic' on very low resolution works compared to high resolution.
But sure, target audience and everything must matter too.
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