First of all, it wasn't guaranteed that this feature of yours would come. Even in this case, the feature came, you could probably add it with not too much effort, sure maybe a bit more than otherwise, but on a large project it's hard to guess the future. What if someone else would have taken that task, maybe they wouldn't even recognize why those columns are there and they could have just reimplemented it anyway.

Also, a year is a long time, and who knows how many times it would have caused additional work and confusion.

> A: hey why this thing here, it doesn't do anything / never actually used?

> B: I dunno, Alex added it because 'one day we might need it' (eyeroll), will get very touchy about if you try to remove it, and will explain how he/she can predict the future and we will definitely need this feature.

> A: and this thing over there?

> B: Same... just move on, please, I can't keep re-discussing these things every month...

And, if your team wouldn't have applied YAGNI, you would have 1 feature that was a year later needed, and probably around 20 that was never needed, yet caused maintenance burden for years down the road.

I dunno, YAGNI is one of the most valuable principles in software development, in my opinion.