99.985% of coding is maintenance*

Maintaining code means changing it.

Those changes could be alterations to what's already there or in addition to what exists.

This isn't only true once a version has been released or shipped.

This is also true during initial development. 

Once there is other code, this needs to be read and understood, and additions/changes made in light of what already exists. 

Whether there is one existing line of code or one million; if what exists is hard to understand and reason about, future alterations to the code can be hard to integrate and risk unintended consequences. Both of which take more time/money. 

Maybe that's not a problem for you, but every developer I've ever met has more things they need to do. More bugs to fix, more features to add, or new products to create. Having more maintainable code means they get to more of those things; and faster!

Optimize for maintenance (ease of reading/comprehension) to save time/money in the short, medium, and long terms.

* Not a fact but an educated approximation.