More time elapsing for any given response/follow-up/appreciation comment to appear seems like it would be preferable to bad responses lingering. Browsing Ceddit you can see moderators remove the junk very quickly most often, but they can't always be everywhere instantly at once and sometimes bad stuff sticks around because its not immediately clear if its a good response or not. OP posting "Thanks for the great answer!" beneath a removed comment is pretty common I've noticed...the much later good answer going maybe unnoticed as the question had already been "answered".
If it would make life easier for the moderators, it might be worth the time-delay for commenters.
From a practical perspective, traffic on the subreddit doesn't generally require that level of moderation - and we don't have enough mods in enough timezones to monitor every new response as they come in. Having ever response automatically invisible without moderation typically discourages a lot of posters from submitting answers, which is the opposite of what we generally want - so long as they follow the rules.
Even if we did engage that kind of moderation, the human work that has to go into adjudicating replies would only increase - as it is, we mainly respond to approving/disapproving posts and what reports that come in, keeping an especial eye on rising threads which tend to get more traffic.