I think people (myself included) are more willing to put money into actual books because getting a book electronically from the SPL is such an exercise in frustration. The process is so arcane and annoying it's not clear to me that putting money into it will dramatically improve things. Plus reading books electronically is making huge gains all the time, but it's still pretty new to most people. I expect in the next 2-5 years this will be a much bigger part of public library's budgets. Hopefully by then they'll figure out the DRM crap that's most of what makes it a fiasco now.
But nobody wants ebooks from the library. The whole point of the library is that you don't have to OWN the books and store them. Ebooks are easy to store, and less fun to read.
Nobody said downtown SPL was a drag on the entire library system? That building is .. unworkable.