I work at a game company and over length of my career interacted with quite a few engine companies. The separation is at where you set the bar.<p>If a game company shipped a game in a state that an engine company does it could only fly on PC and would only take a little while before players would realize that this company ships half-done games and stopped buying them immediately after release.<p>I am not putting down the engine companies, it&#x27;s just the different priorities that both have. A game ships to a consumer who has no way of working around its bugs, an engine ships to a developer who has likely already rewritten half of the engine anyway and, even if not, is able to get back with bugs and request fixes&#x2F;workarounds. For an engine company&#x27;s customers it&#x27;s preferable to get the new features than a 99.99% bug-free build. Game company customers are of opposite preference.