I think the assumption they're making, which is the assumption that I would make were I in a band in this position, is that anyone who cares enough to donate money to help them make a record already owns their pre-existing music in some capacity.
I get that but I mean this is the only one of these things I have ever seen where you don't get a digital download or a cd of the new album when its done. I get that they wanna sell it and that is all good but if fans are willing to give 20-100+ throwing in a copy of the album seems standard. Even assuming the band is going for a full digital only release and no hard copies this time around which I have seen bands do tacking on a digital copy can't hurt them that much especially when it really gives the fans that want this album out so much what they really want in the end. These things are meant to be mutually beneficial. Money is given to the band to record a record with hopes it will be good and rewards are given to the backers for their contribution to making the album release possible.
I will buy the album when it comes out and if the singer asked for a bit of help (I know the guy) I would easily give him a 10 or something but I just don't see the need (personally...not speaking for everyone) to go through this whole process.