Remember who's paying
I'm speaking here as a twenty+ year veteran of the software development business, and -- yes -- I wear jeans (and a smart shirt) to work. I'm now a CTO-level consultant, and also CEO of a set-top box manufacturer.
Although, as Martin comments, Beck wasn't articulating himself too well, Beck has a very good point. Software developers have for a very long time been treated as a species apart: strange, feral creatures that ingest caffeine and extrude code, and operate according to their own lights.
It's suited the developers very well. But it's also insulated them from the most salient fact of their employment: that they're paid to make money for their employers. It's great to feel the aesthetics of the code innately, but if you're spending all day recoding a member function to be blisteringly fast, just because it "looked wrong", and the change makes no impact on the product, you've just sneaked a day's paid holiday.
The jeans-and-scruffy-T-shirt "dress code" doesn't encourage programmers to think business. Unfortunate, since it's business that's paying their wages, and reasonably expects that their every working action is directed towards increasing value in the product.
Ask the average programmer what are the market drivers for the product they're working on, and you'll probably get a blank stare. ("Why do I need to know that?") Yet they are expected to be working towards satisfying those needs. This is a dangerous disconnect, because developers are keenly intelligent people, on the whole, and if they understand the business model, have exposure to the end users, and are (in short) brought into the business, they can contribute massively to its profitability, and direct their own efforts more accurately towards a better product, and a healthier company.
But that requires a shift from both sides. Senior managers need to stop treating developers like quarantine victims; developers need in turn to stop treating work like play. Take a look at an outsourcing centre in India, and you'll see those principles at work. We, in the Western Hemisphere, need to learn those lessons, get a smarter (in both senses) attitude, and get down to work -- whilst there's still work to be had.