I mean...Nobody needs to be taken out and shot or anything, but retakes are possible. It's not like they'd have to do it perfectly the first time.
Retakes are possible if the reader is aware that they made a mistake. If they're not, and it's only caught later, in post-production, then the podcast's ability to chase down the reader and get them to re-record is limited.
Remember, there's a selection bias going on here - whenever there's an error in the podcast that the readers catch, that means it's an error that wasn't fixed. If there's an error that was fixed, we'll never be aware of it. So, presumably, whenever we hear a mistake, it may well be because circumstances meant it couldn't be fixed, and that if it could have been fixed, it would have been.