The idea is not to disenfranchise a qualified voter because of poor geography skills.

Provisional ballots are not absentee ballots. In states which allow provisional ballots, this is what happens:

John Q. Public shows up at what he thinks is his polling place. He believes he is registered to vote, and he believes he's in the right place. His name is not on the voter roles, however. Rather than deny him his right to vote, he is allowed to cast a provisional ballot. This ballot may or may not be valid, depending on whether his registration problem can be straightened out. It will be counted or destroyed, depending on the outcome of the investigation.

How can this happen?

A name can be left off the roles for some bureaucratic reason. It might also happen for a criminal reason, but let's assume for civility's sake that it was an honest mistake somewhere. An investigation can turn up the misplaced record at the court house. Or perhaps the voter can locate his voter registration card somewhere among last year's tax receipts or something. His vote is saved.

Or someone is a new resident of an area, and has registered by mail in plenty of time at the county seat. The registration card comes back with an election precinct number on it, but no location for the polling place. In the welter of local government phone numbers, the new voter locates what is supposed to be the polling place, only it has been moved, say, from the school to the fire hall, but the sign doesn't say which fire hall because everybody just "knows". (Don't laugh. It happened here.) So the polls close at 8:00, it's 7:45, the voter has found the fire hall, but it's the wrong one. He casts a provisional ballot. Everything gets straightened out in the morning, and his vote is saved.

The controversy over provisional ballots isn't the same as the one over absentee ballots, which are very easy to fake and have traditionally been a source of election fraud. A provisional ballot requires that someone be physically present to cast it, as well as providing his address to corroborate any found registration record later. If someone was determined to commit election fraud in this way, he would have to hit all the local polling places on Election Day and vote at each one in person. One hopes he would know that the provisional ballots would all be investigated and that he's likely to be charged with multiple counts of felony election fraud, but some people are too stoopid to think this far ahead.

I understand that South Carolina is embroiled in a controversy over whether or not to allow provisional ballots to be cast anywhere but in the correct precinct. It seems to me that not to allow out-of-precinct votes eliminates about half of the reasons that people have to file these things in the first place. If they knew their proper precinct, or where their precinct's polling place was, they wouldn't have to file provisional ballots, would they? I don't know my precinct number, but I've lived in the same house for close to 20 years so I don't really need to.

South Carolinians are going to have to work this out for themselves.