I actually grabbed GIMP last night using Flatpak, and a few weeks ago downloaded Tenacity the same way.
I'm still unsure what the reason is to use one over the other, but Snapcraft is definitely losing the war of minds online, as far as I see.
I think the actual word is "Apple-ish". Microsoft never succeeded in their appstore attempts, whereas Apple sadly did (and spectacularly so).
I very much do. Software was sold in boxes in independent store chains. Sure, MS abused their position whenever they could, but their various attempts at building appstores they could control never really succeeded, the best they could do is abusing OEMs to preload this or that crapware.
Apple, on the other hand, defined the market for walled-garden mobile appstores, with all their orwellian warts and obscene profiteering. But unlike with nerdy, cut-throat and business-y MS, "the public" loved their hip image and let them get away with it.
Apple did the same with Sherlock (it's even a verb).
But Microsoft had a monopoly (confirmed by a long federal antitrust lawsuit), and Apple did not, so Microsoft rightly gets the blame.
Honestly, I'm all for throwing stones at Microsoft, but when it comes to appstores in particular Apple clearly are the most masterfully evil of them all.
A couple of years ago they were looking to recruit dev advocates specifically for Snap. I applied and never even got a response. I guess they hired the wrong ones ;)
Practical example, I use nextcloud as a snap, which requires basically one command, it self updating, shares the same IP as the host whereas each docker container would have a separate ip. If you only want to isolate an individual application on a host system (which is a common use-case) most container technologies are overkill.
docker run --network=host was available several years earlier than snap.