Piano is in this weird position where for a LOT of material, given the choice people tend to pan according to player's perspective, or LH left and RH right, across a wide stereo spread.
This is opposed to e.g. the rest of an orchestral ensemble or big band where you always pan according to audience perspective, or stuff like drums in band repertoire where wars have broken out w.r.t audience perspective (HH right) vs drummer's perspective (HH left)
I prefer that piano convention as well, even if it's a bit of suspension of disbelief as to its position in an orchestra, because 1) people are really, REALLY used to hearing it that way from the vast majority of contemporary records out today and 2) it actually plays nice when mixing for orchestra, since LH left and RH right means the bass frequencies are concentrated towards the left, which then doesn't fight for the same space as strings bass frequencies on the right. Ditto treble on piano (right) vs highs on strings (left).
edit @ edit: it's not just so much musicians as it is people simply used to the sound of an orchestra generally being seated a certain way. Musicians playing in an orchestra obviously hear things very differently from an audience. (it's always a shit ton of percussion someone send help)