They did reprints of 1e and 2e a few years back (not sure if they did 3e as well). I don't know how well they sold, but I'm pretty sure Wizards does, and I'm also pretty sure that if they had sold like hotcakes they'd still be selling them. They're also for sale as PDFs via DM's Guild, for $10 each, with options for POD. A friend of mine got a copy of the Rules Cyclopedia this way (though I don't know if he's used it).Or just dust off any of the previous editions, and if they truly wanted to milk all the profits possible port them into a DDB that works properly with them.
Talk about low hanging fruit.
And porting them into DDB or a similar system would likely be out of the question – at least the mechanical parts of it. The text, sure, but there's no way there's enough money in making a 2e character generator – particularly given the myriad variant rules which would make programming one a nightmare.