Does anyone know why collected editions of Swamp Thing at only available as trade paper back and not on comixology. Is that a Dc issue or an Alan Moore issue?

A very small percentage of anything old is available digitally, so I don't think it's anything contractual or unusual in this case.

They still haven't released the pre-Moore run of Saga of the Swamp Thing right? 1-20? I know it's not essential, but would prefer to read that first.

20 is the first issue of Moore's run. It just wasn't collected with the rest of his issues until recently because it was more of a wrap-up issue for the previous run.

Oh that's right. I think my version is the one missing #20, but a newer version included it. But still no 1-19 anywhere but floppies right?

All 24 issues of the 1972-1976 first series are on Comixology, the last 11 in B&W for some reason, but at 99 cents.

The first 77 issues and second annual of the 1982-1996 run are on Comixology, the first 'Saga' issue at 99 cents.

And all 25 issues/annual of the new 52 run are available.

Just to clarify my simultaneous post: No, they are there on Comixology, but sort of hidden at the end of the 1982-1996 listings as they were technically titled The Saga of the Swamp Thing.

But why would they only be offered as single issues and not as collected editions?

Thanks

Basically it's back to my first answer. Relatively little of anything is actually available.