Yeah, not long ago on HN I read into somebody who really wanted a type that's a list of blocks which expands and shrinks only by whole blocks. Such a type would have amortized O(1) push at one end, like Vec, and also amortized O(1) pop - but with much smaller and more frequent allocations, and the index access is horrible, but it would only ever be over-allocating by a bounded amount, this is a relatively inconvenient type for a lot of purposes which is why AFAIK nobody provides this out of the box, but it did suit their needs.

Lest people imagine Rust has so few collections because nobody offered any others, Aria has a rant in her Linked Lists "tutorial" where she explains that pre Rust 1.0 she was cleaning out all the miscellaneous collection types few people need - and she tried but failed to remove the linked list type. There's some very niche types in her list, things I've heard of but never used in decades of professional software engineering.