Let's not forget the relevance of the bottomless pits in the classic games, too: for example in Wing Fortress Zone, while the level was suspended over a bottomless pit, the only times you were in danger of falling into it was when you were hanging and navigating between bars right on the bottom of the ship, which added to the suspenseful feeling of being somewhere very high up and right underneath the ship. Also in Sonic & Knuckles' Death Egg act 2, one or two bottomless pits right at the bottom of the level (but not unfairly placed) also gave the player a feeling of being at the bottom of the ship, suspended over an unforgiving gateway into space.
Flying Battery and Star Light also did this well, and it was always the player's fault for falling to their death because the situation made it clear there would be nothing below to stop you.