For deppy, their relationship has been discussed probably since before they met, over and over again. There's speculation everywhere, we on here have threads and compilations and screenshots too, and it comes up again and again in the main thread, and everyone has their assumptions and interpretations.
With a background like that, maybe if you decided you wanted to share a relationship, you would want to do it in a way that does it justice. Meaning, you would want to carefully choose what to show, maybe you would want to explain how everything came about and share the entire journey to make everyone understand why you did things the way you did.
Because, imagine this: They might have been together since 2009, and they told that now, just randomly in a video or whatever way you can think of. There would be backlash too, a lot of it, probably. "You have lied to us" "but what about 2012" "you said [grandma comparison]", people would dig it all up and accuse them of things. Maybe, if you had decided you wanted to share that, you would also like to tell it piece by piece so maybe more people understand why you're only sharing now.
Or maybe, it would just feel like such an important thing after so long that you want to display it in a high quality and beautiful way, because you're excited to share it properly.
Those are just some reasons I could imagine why someone would want to do a bigger production than a simple YouTube video.
And why shouldn't that be paid? There goes a lot of work into such a thing; of course there needs to be something that comes out at the end of it for those who created it. And, they get paid for YouTube videos too, it's just not our specific decision to give them money and you can watch it even without paying.
I just want to provide justification for deciding to share big things like this in a way where people have to pay. You might want it to be yours only, you might want to do it properly, and of course you'll need your efforts to be weighed up.
And I don't think they have an obligation to make their relationship the easiest thing accessible, even if they choose to share it. A fandom still doesn't have the "right" to have free and open access to it; that's not something you can expect from a creator, in my opinion.
Especially since the information will obviously be shared in the fandom and they would probably address it on their own if it was prefaced by a big coming out event. You got the info, if you want the high quality stuff that a lot of work went into, you'll have to pay for that high quality stuff.
All of that being said, I don't think that's a thing deppy would do, because fancybum really pointed out great reasons why they probably wouldn't want to. I just personally find it justifiable if they would want to after all.