Being a small drop in a big glass of water comes with its own, albeit different, motivation. Small projects that one person, or a small group of people, can fully own are necessarily limited in scope.

Personally, I don't dream of having full ownership of my own successful little project nearly so much as I dream of playing a relatively small, but necessary, role in a big ambitious project. For me, this[0] is the dream. Look at all those elated drops of water! I think the Fleet Foxes put this pretty well in "Helplessness Blues": "after some thinking, I'd say I'd rather be a functioning cog in some great machinery serving something beyond me".

Having said all that, my point isn't that all big projects are better; obviously not every project is literal rocket science, and all else equal I find ownership more motivating as well, it just isn't the only thing that can be motivating.

[0]: https://youtu.be/ANv5UfZsvZQ?t=127