Doesn't matter what the code looks like, as long as the customers
are happy.
"It doesn't matter what the warehouse looks like, as long as we ship on time, and the customers are happy."
At one level that's true, but at another level, it does matter what your warehouse looks like, because a neat and tidy warehouse is what allows you to ship on time. A warehouse that's filthy and disorganized is one which loses orders, ships the wrong products. Similarly a disorganized codebase with poor abstractions isn't bad because it's unpleasant to work in. It's bad because when a dev ships a feature, they have little or no confidence that they've done so without breaking two or three other features and causing customer dissatisfaction in the process.