I thin being able to actually have some benefit from the releaseData field (like sorting, export) would motivate people more to fill it in.
Also as it is now you don't even know where the field is missing if you don't iterate over all the games.
Well, no one person is going to go through and add the release date info to titles. I know a lot of people won't bother with that because they don't care. So it's up to the people who care to go and update that info. But yes, I agree.
I don't believe this is a difficult addition to the export function, Matt did it before on a previous request of mine to add the VGC Id.
But once it is included, assuming it gets included, you'll be able to look through your collection and see what doesn't have release date data and you can go submit edits.