I've been experimenting with running Ubuntu on an old Macbook and was happy to find a lot of my old games already run on Linux though the Linux version of DOSBox.

But looking further, many more of my games that use DOXBox don't have a Linux version.

Is it just a matter of not being done yet? (Such as not enough votes on the wishlist?)
Or just something they expect us to set up on our own?

It just seems like an easy way to get a lot more games to their customers, but I do know they are busy with lots of projects.

EDIT: I do see a wishlist item that mentions this, but not a lot of info on why.
It does seem like it isn't had to do on one's own after some research.

Laziness and licencing.

Yes, some do insist of having separate licencing for each operating system.

Seems like a silly problem.

Ah yes, I wouldn't be surprised if licensing is part of the issue.