You could literally only have "hash table" and this would be true for "necessary for the majority". But maybe we should raise the bar a little bit.

Necessary? Maybe not. Useful? More often than you'd think, in more domains than you'd think.

Basic probabilistic structures like bloom filters and the hyperloglog in particular are severely slept on.

Forget probabilistic structures, any intro to data structures that doesn't show you a deque built with a ring buffer is shit, and I'll die on that hill.

(That being said, I'm tweaking something in the ASketch family as we speak, so I agree 100%.)