Value Proposition
You mentioned DDI:
Even better is the WotC approach with the DDI, you can look up any
monster or item or (almost any) rule, in the most recent form, for 3
years at the cost of seven books. I think this is the way to go, even
considering the horribly slow character builder.
It's true, for three years that is a good deal. But what about for six years?
I'm still using my 3.5 PHB, ten years after I got it. I have a set of 3.5 books that is nowhere near the full quantity they released, and I'm okay with that because I don't care about a lot of the books they put out.
If DDI existed for 3.5, it would have cost me more than I paid for the books rather than less. Being an upfront cost, books don't cost more if you use them for longer. Subscriptions do.
And of course, online services disappear every day. Will DDI for 4e still be around in 10 years? If you want to play and it goes away, where did your rules go? I own a book from the 1800s, so I'm pretty confident that Wizards can't take my 3.5 paper books away should they decide it's time to move on and not pay for servers anymore (or go out of business).
Page Flipping & Sharing
I have bookmarks in my PHB & DMG. I also just know where some things are, because I've had to use them so many times. I can open the book and be in the grapple rules in two seconds. No matter how hard I try, I can't get there that fast on my iPad. I also can't have the grapple rules AND my encounter notes open at the same time with the electronic version, since my iPad can only show one thing at a time. With the books, I can put them beside each other. I can then also add a spell description from the Spell Compendium. The area around me when I DM tends to look like a book fort.
It's easy to share the book. I can hand someone my PHB so they can look up a spell description and keep doing what I was doing with my other books & iPad notes. If I have to hand them my iPad, I just lost access to everything until I get it back.
Subjective Stuff
There's a subjective side to this as well. I like how books feel. I find them easier on my eyes than ebooks. They work at the cottage, even with no power.
In the end, it's really about which trade offs you prefer to make.
Yes, they had a problem with the glue they used for the first printing, is my understanding. Our first PHB was falling apart within weeks. We called WotC and they sent a Fedex call tag to pick it up, and replaced it for free, but it took 3 weeks, door to door. It wasn't the whole first printing that had problems. The replacement that we received was also content-wise the first printing (un-errata'd) but had an obviously more flexible glue used for the binding.
Our FLGS owner had originally been told that Wizards would only deal directly with customers, and not with him, regarding the defective books, which is why we went through Wizards directly. But when I told him that I'd read online that other gaming stores were able to replace the book for their customers, they called and asked again and were told that they could indeed replace defective books and would be compensated for them.
So, in the interest of not being without your book for 3 weeks, if you bought it locally, I'd suggest bringing it back. If they still copies in stock, you should be able to exchange it right in store.
Best Answer
This is actually an intentional strategy on the part of WOTC. Obviously we don't have full insight into everything they are thinking, but Mearls did talk a good bit about the intended release schedule in the run up to the release of the edition.
So part of the reasoning in creating limited releases is that the feedback they got on the playtest indicated that their customers wanted limited releases.
At this point it looks like those releases won't be splat books, but will generally be drivers for their organized play events (The current event being ToD and the next one being a single book Elemental Evil campaign).
More importantly, the kinds of things you're looking for, will likely at least for starters, be published digitally, and take a long time to develop. For instance, if you were interested in Eberron, they have already published an Eberron playtest for 5e.
They've said in a few places (including the AMA linked above, here's a better digest), that they plan to release a lot of optional content, and potentially other things (like the setting materials you mention maybe) via their website rather than to do full publications for it.