That's an interesting question... I'd love to see an L-Frame .41 magnum.
Depending on which website you look on, the max average pressure specs for the .357 and .41 mags are seemingly not too different.... but would a 1,000 PSI difference enough of a difference to make it not at all feasible in a L-Frame?? SAAMI has lowered the pressure specs from what they were originally, probably as a liability concern, but if a particular frame was originally engineered to withstand the higher SAAMI levels... things could be "close enough".
.357 mag SAAMI is 35000 PSI (originally 47,000)
.41 mag SAAMI is 36000 PSI (originally 40,000)
Jeez... if S&W can get a Model 640 J-Frame to shoot .357 mag, you'd think it would be somewhat a walk in the park for a .41 Mag in an L-Frame.
As for S&W not trying to do it... that may be just an issue of economics, with the .41 mag cartridge considered as not being enough of a seller to warrant it... we've seen S&W drop models from their catalog over the years for the same reason.