I'm not saying I hate them, I find it sill that people complain about a design element in one platformer while praising its inclusion in another, more adventure-based game. I have never found a spike or pit in a Sonic game particularly unpredictable, they scale well with the difficulty of the game. Even if platformers MUST include such elements in order to be a part of the genre, many actually don't use them because they're considered cheap. Again, Sonic was a specific example, and one that I don't even think features all that many bottomless pits.
But the predictable nature of their placement in Shovel Knight (as in, you know there's going to be one since they're EVERYWHERE in the game) and their inclusion in Plague of Shadows highlights the trappings of the game's initial design. And it does not have limitless saves and checkpoints, since the loot system limits replays. What is more annoying about the loot system is that recovering your loot is actually sometimes an impossible thing, which is again facilitated by the design of the levels.
You know, Mutant Mudds is one of my favorite platformers. Period. And it also features these elements, including instant-kill spikes. But the thing Mutant Mudds does is it freezes the character upon taking damage, which instantly creates a mental picture in the player's mind to remember situations such as those, or to be more cautious in those circumstances, or even try a different approach. Shovel Knight uses a recoil system which sends the character on a predictable arc but one that can react very differently given the design of a level- and more than often ensures death. I understand people enjoy beating their heads against a wall, especially in action/adventure games such as these, but I guess I will never understand or appreciate the reason why. It's aggravating to me, and it doesn't make me want to keep replaying the same instance over and over when I know there's about ten different ways I can be screwed over by one design element in a stage just because it has an abundance of pits close to it.