Depends on what you are going to keep in your tank. I have a 60 gal FOWLR and do fine with just my LR and a cannister. I only have a five fish and 4 are pretty small.
So, no, I don't think they are necessary. That being said, I think they are convienent and nice to have. Easier to make changes/adjustments and hide equipment in a sump.
lisa