I think people underestimate how much maintenance work there is today. iOS alone adds features yearly that everyone expects the existing apps to support on day 1. While macos has fewer changes, same issue there.
And calendars...smh. It would be great if MS and Google both followed some standard perfectly, but based on what I've seen from various calendar apps, they do not. Otherwise, the apps would not have such a hard time dealing with multiple calendars.
The basics have been standardized many times. People who pay for something like Fanstastical aren't looking for just the basics - delegates for example. ICal also support vendor extensions that need support.
HN of all places is one I wouldn't think would assume software maintenance is easy. But, it's where I saw people complain about the Uber app size until an Uber engineer showed up and explained the many screens for payments alone.
And calendars...smh. It would be great if MS and Google both followed some standard perfectly, but based on what I've seen from various calendar apps, they do not. Otherwise, the apps would not have such a hard time dealing with multiple calendars.