The problem with “denylist/allowlist” is that the semantics of “blacklist/whitelist” are broader in practice than what that can convey.

In the general case, blacklists and whitelists relate to operations on non-enumerable sets. In particular, blacklists and whitelists are not invertible, due to that non-enumerability i.e. you can’t generate a blacklist from a whitelist nor vice versa. So whitelists exclude a non-enumerable set and blacklists include a non-enumerable set. It is a useful concept separate from purely enumerable sets.

Many uses of whitelist/blacklist in practice have nothing to do with “allowing” or “denying”. You can use some explicit set inclusion/exclusion term but that isn’t nearly as concise and everyone already knows what a whitelist/blacklist is.