Closed captioning is insanely expensive. For longer seasons of shows, it can cost anywhere between $5,000-$10,000. In some cases, like Super Mario Bros. Super Show!, my budget AFTER authoring was probably somewhere around $2,000. It's just not possible.
And no one really seems all that interested in donating the captioning costs. We've actively sought folks willing to pay for it, in exchange for "advertising," but no one has bitten. When Goodyear Tires sponsors closed captioning on a TV show, they only do so for the broadcast of the episode. And they do it because they get featured ad time.
For those saying that the captioning file exists, so we should simply use what was run with the broadcasts, unfortunately, you're wrong. The two file formats are incompatible. I cannot put a broadcast CC file on a DVD and expect it to work. So I have to get it reformatted, which is cheaper than having the file created by scratch, but not by much.
And here's the kicker... The unfortunate truth is that we know how many people bought the sets. What we don't know is how many people DIDN'T buy the sets. For any reason. Maybe they picked it up and didn't like it. Maybe they didn't like the imagery on the box. Maybe they didn't like the way the back-of-box copy was written. Maybe they thought it was one show instead of the other. Maybe they were deaf and didn't see the CC symbol on the packaging. There are no solid numbers or data that definitively says how many sales were lost due to the lack of closed captioning. Because even if it was closed captioned, it doesn't mean the hard of hearing would automatically purchase it.
We're trying. Hard. We think most--if not all--of our sets should be CCed. And we're making all the moves to get as many of them CCed as possible. But until we're provided with the funds used to cover the cost of closed captioning, we just can't make those promises, especially on titles we don't expect to sell thousands upon thousands of. The money simply isn't there, no matter how many fans complain. It's not a matter of "we have it, but don't wanna spend it." We just don't have it for every title.