Most probably these are exchange wallets or secondary hard wallets from exchanges. Remember that exchanges keep more than one wallet. It is not a good security practice to put all funds in one address.
these addresses are too randomly chosen by OP to just show a list of addresses, they could have had 0 balance for all OP cares (as most of them do). he was just trying to create a topic with a weird title!
as for keeping it in one address it is not such a terrible thing to do in my opinion if that one address has sufficient security. and if anything you can use a multi signature (1 address with multiple keys) but keep its keys separate.