Just like Theft is factored into a place like Home Depot, Piracy needs to simply seen as a cost of doing business....
True. Total elimination of piracy is a pipe dream, as much as 'totally error free' or 'no down time', and other ideas. It's always important for a business to accept a certain level of negatives will slip in, and instead look to ways to both minimize it, and mitigate against what is left over.
This does not translate to doing nothing to deter piracy. Companies that factor theft into the accounting still do things to stop thieves, catch thieves and deter thieves.
The WOTC official pdfs made things easy for pirates, so eliminating the one thing that contributes most obviously to piracy that they can control seems like a simple step.
A rational reaction to pirating isn't to make it
easier for your product to be pirated. They could just put the pdfs for free effectively making piracy a moot point. Or they can stop producing the pdfs
for the pirates. Selling the pdfs is equivalent to the first part, and just asking for fans to "do the right thing" and pay for something they can get for free.
DDI isn't 1 to 1 equivalent to a pdf, but it covers a lot of the same areas in terms of fufilling needs. Thus, it
does compete with pdfs, both the sold ones and the pirated ones, even if some prefer one to the other, or would like the benefit of having both.