That leaves you with no way to check to make sure you entered the right term, other than typing it again. If you are typing it right but auto-correct is kicking in when you hit enter, even trying again might fail because your site responds fast enough that you might not have time to notice the change before the results page comes up.
Also, it might be helpful when someone searches for a domain at a TLD that you do not support to say on the results page that the TLD is not supported.