To be fair, the same can apply to many, many different situations. As far as I'm concerned, accidentally edge-canceling and airdodging to your death isn't much different from shielding a move near the edge and not realizing the move was powerful enough to push you off the edge, then trying to retaliate with an attack and using a N-Air to your death.Also, you don't want to L-cancel when you edge cancel a move (assuming this isn't brawl) elsewise you'll **** up and accidentally shield as you're letting go of the shoulder button. And edge canceling CAN happen accidentally, so it requires more knowledge on the player's part about exactly when they would edge-cancel..
To me, it's the same required knowledge as "don't do an attack while offstage if it will prevent you from being able to recover." The situations are just as risky (you lose a stock for it), and you often have to ask yourself if it's a good or bad idea in the heat of the moment (the pressure builds; there are good reasons to do either option at the right time).
Also, that's only one very specific place where trying to L-Cancel might not be such a good idea (which can also be reasonably negated completely just by knowing the distance exactly), whereas other comparable option selects have a much more balanced risk/reward set overall.