This is such an astonishing waste of resources. When I start a new game, I spend 3-4 months rewriting the worst or most dated part of my engine, and then I take that old (but solid) engine and make the coolest story I can with it. It's a small company. Our resources are desperately limited. Thus, I don't spend time remaking things that already work. If my wolf icon looks good, why make a new wolf icon just for the sake of making a new one? Instead, I focus on the story, the one thing that truly needs to be all new and excellent.
And the big companies, who make AAA games with these amazing awesome big-budget engines? They should re-use more of them! The Dragon Age engine is very cool. Make ten games with it! And not just piddly Dragon Age DLC either. Make games that are cyberpunk, horror, science fiction, fantasy in a new setting. The budgets will be much lower, and that makes it easier to take risks. And use the same dragon model. It looks really sweet. And, once the engine is a drained husk (in, say, five years), then spend a lot of money making a new one.