The thing is that such features can also become a burden quickly. E.g. people know it is not used, so nobody bothers to write tests or other things that would be usually done and those things might come back to haunt you once it is and boom a good source for catastrophic failure is there. Also, when you implement it later you can shape it without having to rework a ton of code.

Don't get me wrong, I understand your point here — and if the feature is something that you know for sure will be needed later on, adding it in from the start instead of bolting it on later is absolutely the smart choice. You wouldn't pour a concrete foundation for a building after you built two floors — especially if you know from the start it is going to be a skyscraper you are building.

In fact my experience with software development is that good foundations make everything easier. The question is just whether the thing we're talking about is truly part of the fundament or rather some ornament that can easily be added in later.