Can you give an example of where this happens?

In my experience a well-factored program means that you always have a codebase that is flexible enough to accept new features simply. However large.

There is also the advantage of avoiding the overhead of infrastructure until you need it, which means you have a smaller simpler codebase that is faster to develop and maintain.

Look at the older code for everybuddy. It's in C. They don't do anything with any idea of expanding on their source code, till now. You can't even do drag-and-drop withtheir current code base. It'd requier expert knowledge in the code to know HOW to refactor it.

Incrememnttal is always good and all, but planning against extending or expanding is a shot in the foot.

Yes a lot of old code is in C, and a lot of it sucks quite badly.

However, that's not the issue is it?

I thought we were talking about whether adding infrastructure upfront that isn't needed until later is more/less efficient than adding the infrastructure at the point it is needed.

My experience (and the experience of others - well chromatic at least :-) has been that the latter is a far better approach. You're not guessing at the requirements, and you don't have to carry the overhead of the extra infrastructure when it isn't needed.

Nobody is "planning against extending" - just choosing not to extend until it is necessary by an actual requirement.