Yes, it does. Bad architectural and engineering practices will start to burn you at a couple thousand lines of code. "Maintainability" isn't some far-off property that begins to matter when you're at hundreds of thousands of lines.

For the record, the best way to learn software architecture (what works, what doesn't) is to maintain your own code. Only when you support a project from inception to maturity do you get a sense of how much architecture matters and why it is so important.

The question is more of is it required. I want to see weather there are many companies that have created hard to maintain code, but were able to become successful because of just producing a product that people wanted.