However, if they had given it more time, they can receive more answers that may be better than the original.
Your question makes sense, but you're assuming that accepting an answer would somehow discourage users from posting new answers. Based on my experience, I don't think there is very close correlation between the two. The warning is not necessary because
- You can change the acceptance whenever you want., as the help center says:
You may change which answer is accepted, or simply un-accept the answer, at any time. You may change which answer is accepted, or simply un-accept the answer, at any time
Accepted answer doesn't discourage users (especially those with enough experience) from posting a new answer.
It's a way of saying "thank you" for some users. We can't warn the OP against this graceful gesture.
You need to note that there are many users who post just one question and never come back after accepting an answer. Also, there are those who don't even know what acceptance is and how to accept an answer. Only experience and time spent on each site will help them.
The more important issue is how to differentiate well-researched and useful answers from under-researched and unhelpful answers. If upvoting and downvoting work in the way they have been designed, we don't have to worry about this acceptance issue.
