The political class does not take kindly to being mocked.
Although, at least in Franken's case, they don't have any qualms about mocking others.
Well, of course the idea of not voting in a particular race on a ballot has occurred to many people, and it'd probably be simpler to just have folks leave it blank. And that would preclude the problem you mention, but that still leaves the problem of what to do when legitimate write-in candidates exist. Having ballots prepared with an "other: ______ " option available is a cost-effective and sensible way to deal with the problem. Otherwise, you'd have to change write-in candidate rules in a way that they have registration deadlines that occur in time to have ballots printed. But if you're going to do all that, then why would they be a write-in candidate in the first place? You could have their names spelled out properly if that were the case.