Distributors I know. BTW I'm not trying to make a big thing about piracy here, hence my off-the-cuff remark. But it's just basic economics - there's a fairly small but non-zero cost of doing a DVD issue even if its a rerun and some films just aren't going to earn it back.
Bear in mind that many, many films would not be profitable on their own, but are cross-subsidized by more popular films in package distribution deals, especially international ones.
DVD production for non-mainstream films was an iffy business at the best of times. Sales figures for even a company like Criterion were MUCH lower than you might expect. It didn't take much piracy to destroy what was already a marginal business.
Source- Friends who went out of business as the market died. And industry sales report data that showed the small size of the market to start with.
Source?