I would say it depends on the update. Bug fixes and things that should have reasonably been included in the original game? That's a right. New content, new items, new bosses, new features that redefine gameplay, etc? That's a bonus.

Like, let's say there's a feature that was shown in advertisements but wasn't quite ready for the launch date. That's an obligation; the company simply being expected to deliver what it promised. Some people likely bought the game contingent on knowing those features are on the way. I myself bought Kerbal Space Program 2. I loved the original and really wanted to help them continue their work. Hell, I met most of their dev team at a game con. But when I bought the game, I bought it not because of its features at launch, but because of all the features they were promising to implement. I feel really cheated after they shut it down before the game was finished. Sure, they delivered a nominally functional game, but it didn't even match the scope of KSP1, let alone all the advertised features. And the thing is still a buggy mess. I do consider it an obligation to deliver on features you've promised. It's also an obligation to deliver a game that is reasonably functional and free of bugs.

Compare KSP 2 to two other games I've played, No Man's Sky and Satisfactory. Those games not only delivered on their original promises, but have kept making new content for years after they delivered what they promised. Any new features on these games are something I consider a bonus, something I'm joyful to receive, not something I feel obligated to receive.

I agree, assuming the game was released reasonably "complete" and with a minimum of bugs the first time. Or in other words, if the devs were held to the same standard as they were back in the '90s, when games got mastered to physical media once and routine, easy bug fix updates weren't a thing.