I think the point is also to keep 4-star heroes (and even 3-star heroes, to an extent) viable longer and competitive for folks who don’t have as many (or any) 5-stars. As the game expands and there is more to do, you have to strike a balance between folks with deep benches of 5-stars and folks with solid benches of 4-stars. If you make it so difficult that you can’t complete without 5-stars, you’ve essentially paywalled part of the game.
I’ve been sitting on wizard emblems for Onatel, but I also don’t have any better wizard options right now. I wouldn’t be in a hurry to strip emblems from, say, Gormek to put them on a 5-star barbarian like Azlar (although I’d love to have that option! ) For the same number of emblems it would take to max Azlar, I could max Gormek, Grimm, and one more four-star barbarian, I believe. Which has more long-term impact?