You certainly could ask that question, a legitimate one, and I bet you most people don't own enough altcoins such that it would be a pain in the ass to keep track of all the private keys.  Not to mention if your goal isn't long-term storage or if you plan on making some trades or whatnot.

Excellent points of advice, OP.  I followed exactly zero of them when I bought my Ledgers (and that damn Keepkey), but since I don't actually have much of value on them, I'm not terribly worried about getting phished, hacked, keylogged, or whatever else it is that thieves are doing these days.  Lately I've been more of a by-standing cheerleader for bitcoin than someone who's got his foot in the market.  Oh well.

Oh, and if long-term cold storage of bitcoin is your primary goal, I'd say you definitely do not need a hardware wallet....but they're so neat, I probably wouldn't even follow my own advice if I had bitcoin I wanted to keep in cold storage.  I'd probably end up buying a Ledger all over again.  Lol