A developer with a short deadline is going to design things differently than one with a longer deadline. That superior design can often result in better long term maintenance.
There's also the idea of requirements gathering. Some people take it for granted, but if your developers aren't in a position of power in your company, they can't insist on good requirements for software. I've experienced this firsthand.
I once worked for a company in which the field engineers brought in a large chunk of the money for the company. They were the "big dick swingers" in the company, if you will, while the software development team was an attempt at the company to automate a lot of the work done by engineers and then sell services with the gathered data.
This presented a conflict of interest in that the software would have actively made the company need less engineers as they could do their job faster, but because of the two groups relative status within the company, there was no way for the software team to insist on accurate specifications.
The day I walked out of that company I had been asked to rewrite a module of the software for the 3rd time and requested written documentation. I was on the phone with both my manager and the engineer we were supposed to be coordinating with. The engineer flat out refused and told me I didn't need it. I asked him how many years of software dev experience he had.
That's one anecdote, but the point is, politics in a company severely affect the performance of developers and not simply because of testing. I honestly think that's an awfully naive view of the world.
