Probably one month after the book release so that they can maximize the books sales before people start sharing the pdfs.
Well, it sounds like people are sharing the Starter Set PDFs already and they have not even released the PDFs yet. So much for that plan.
All this does is anger the people who want to purchase the PDFs as they are being treated like second class citizens.
..Ignoring the sarcasm..
1. Are you sure that you are not confusing the Starter Set with the Basic Rules PDF released by the company for free? http://www.wizards.com/dnd/Article.aspx?x=dnd/basicrules
2. Books in PDF format are notoriously easy to pirate and distribute. You need to direct your anger more towards the unscrupulous people who enjoy pirating such materials. While they may be a small minority of PDF users, they often do enough financial damage to companies for them to postpone PDF releases in order to minimize their potential losses.
I think the plan for 5E is to make PDFs of the core books, along with everything else, available inside the morning star app
Except that the model that enables Paizo to support the sale of PDFs is really their overall subscription model. They have significant numbers of their customers buying into product line subscriptions which bundle PDFs and print products. Those are direct sales for Paizo so there isn't a reseller involved, and I presume that means Paizo keep more of the selling price as a profit.I don't know if its a problem of scale, but I don't see why D&D can't follow paizo's model. Heck, even bass ackwards GW makes electronic (overcosted) versions available when they do a new release.