A game can have no ending because it's an endless grinding treadmill (like most pay-to-win mobile games and their most satanic incarnation, gacha games, where t

A game can have no ending because it's an endless grinding treadmill (like most pay-to-win mobile games and their most satanic incarnation, gacha games, where they endlessly introduce new characters to milk the player base for money) or it can have no ending because it's a sandbox where you can make your own story, like TES Daggerfall or Ultima Online (Daggerfall did have a main quest with endings but many players choose to just live their life, buy houses, become the leader of factions and so on). Then there are also games that do have a restricted length but they generate very different stories so they have almost endless replayability, like Civilization games or (if I may digress a bit into a totally different thing) AI Dungeon 2. In the former kind of games, indeed infinite length is not an advantage, but I think in the latter two kinds, it is.