That's not the only alternative.
Print books.
DDi.
A potential customer of Player's Handbook II might rank his options as follows:
1) Wizards quality PDF copy of PHB2
2) Print copy of PHB2
3) Pirate PDF copy of PHB2
4) DDi access to PHB2 rules.
Now, if the pirates provide #1 for no cost, that customer goes with that. But with that option gone, it's on to actually buying the PHB2 (as the customer doesn't like the quality of the pirated PDF as opposed to the professionally created one).
Obviously, this is one of many permutations - there are plenty of people who would reverse 2 & 3, and only stopping piracy altogether will get rid of that option!
I don't know how big the pdf market is - I would guess an order of magnitude smaller than the print market at the very least - but when access to better-quality PDFs also eats into the print share of the market, it gets a lot more serious for Wizards.
Cheers!
That's 4E. For 3E material there is:
Buy second-hand print copy.
Download pirated pdf.
Neither alternative makes WotC any money. Stopping the sale of 3E material was not done to battle piracy.
Yeah, yeah, yeah, IANAL etc. My point is: it may have something to do with the legal case. We don't know the whole story here. It is certainly possible.
2) Promises will be made that older material will appear in DDI at some unspecified future date. This alleviates the nerd rage and is the "I'll never beat you again" phase of the spousal abuse syndrome.
No, I'm suggesting they might beidiotsnot up to speed on the issues surrounding piracy, and still be living in the 1990's.
That's not the only alternative.
Print books.
DDi.
A potential customer of Player's Handbook II might rank his options as follows:
1) Wizards quality PDF copy of PHB2
2) Print copy of PHB2
3) Pirate PDF copy of PHB2
4) DDi access to PHB2 rules.
Now, if the pirates provide #1 for no cost, that customer goes with that. But with that option gone, it's on to actually buying the PHB2 (as the customer doesn't like the quality of the pirated PDF as opposed to the professionally created one).
Obviously, this is one of many permutations - there are plenty of people who would reverse 2 & 3, and only stopping piracy altogether will get rid of that option!
I don't know how big the pdf market is - I would guess an order of magnitude smaller than the print market at the very least - but when access to better-quality PDFs also eats into the print share of the market, it gets a lot more serious for Wizards.
Cheers!

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.