At least for second time and beyond playthroughs it should have been added. On players first playthrough I imagine the devs thought if players accidentally skipped cutscenes they wouldn't know where to go, which ironically is what metroid is all about. Or used to be...
You can also go back and check the mission objective again if you forget. And get a review of it on the pause screen. Both of those seem like they would remove any problems from skipping it, as long as the players are aware of them. I don't recall any explicit mention of either, so really, the developers would have done better to just add that and make them skippable.
