@Ozzy47 of course is right about the mistyping, however several boards that I have setup we use a mufti-stage registration system. The first stage we wanted them to log-in as fast as possible and extract only certain parameters from the user for data gathering (10 second registration). This data is then used to help qualify the user in second-stage activation when it is required. Users do not mind 10 seconds, they seem to hate 30 seconds. I have no idea why.
After polling our users, desktop users tend to use cut and paste anyway as they are afraid of inserting errors. The default vbulletin email check is done on form submission and not by JavaScript comparison or via an AJAX call. Mobile customers hate it even worse, although the comparison is advantageous for them as @Ozzy47 has already suggested.
Anyway, my point being that I totally understand the need to be rid of it. If you do rid yourself of it, you better have a secondary check somewhere, by some method.