I'm trying to understand why lists matter. Yes, there are some oddities where some base constructs don't play as well with hashmaps as they do with lists, but it is far from difficult to work with a hashmap. Or an array. What difficulty are you talking about, specifically? (Genuine question.)

Biggest difference I know of, off the top of my head, is the LOOP macro having constructs that care which one you have. Curious if there is more.