Right, I thought there was a lot of older stuff, but Hussar says: , which implies not a lot of older material.
Actually, there was a TON of older material from OD&D, AD&D1, AD&D2, and 3E. It was not complete and comprehensive, but there was a LOT of good, classic material. However, much of the pre 3E stuff was poorly scanned copies of the print products. Which I gladly paid about $4 a pop for at the time . . . . but if WotC simply took those files and allowed a POD option, they resulting quality would be crap. And it would be more expensive than hunting down a "real" copy online. WotC doesn't want to release a crap quality product, because they are well aware of the internet (and real world) rage it would generate, despite the voices crying out for a return of the PDFs.
Even forgetting about the POD option, WotC is currently not willing to release the crappy quality PDF files even for solely computer-based use. I personally wish they hadn't taken that option away, but I understand a company being uncomfortable with selling crap quality products. Especially adding in the problems with piracy, time/money investment (and if you think the time/money investment is nil, you are ignorant), and the worries that it would not be profitable.
I want the PDFs back, you (the rhetorical "you") want the PDFs back, but I can't fault WotC's decision to pull them and rethink how (and if) they will release older products.
I do think that WotC will eventually release digital versions of their back catalog as well as the current game, seeing as most of their direct competitors are doing it, as are similar industries like the comics companies. But I don't think it will be PDF files, but something more easily controlled, like a web app similar to Comixology or something. I hope it will be soon, but WotC, despite being a part of Hasbro, is not a huge company with infinite resources, and they are slow with this kind of thing. I'm okay with that.