Why does Pennsylvania not allow processing of ballots until Election Day?

[DeminPennswoods]

15. It's the law. Before this year, we had strict absentee ballot rules

When you applied, if you were physically unable to go to the poll, you had to provide the reason and your doctor's name, presumably for potential verification. The only other excuse was that you would be out of town on election day. Otherwise, you had to vote in person.

Last year in a great compromise, the state legislature (R) made voting much easier by allowing no excuse absentee voting. In return for that Gov Wolf (D) agreed to eliminate the check box for straight party voting.

Prior to this year, election boards just didn't get that many absentee ballots to process.

Wolf has been trying to reach a compromise with the state legislature to allow for early start to canvassing (doing all but counting), but they couldn't reach an agreement.