First and foremost, a developer is concerned with, passionate about, and even in love with technology and, particularly, his creative expression through technology.  Thus, a developer's primary concerns and interests are not the business' but rather how he can best express his creativity through technology. 

Taken to an extreme, you have folks who are tasked with creating software to meet a business' needs that instead take such tasking as an opportunity for them to play with the technologies that they want to use.  Instead of looking for a technology to suit the business need, they look for a way to make the business need suit their technology.  Similarly, when faced with a question to build or buy, the developer will always choose to build for the sheer joy of making software, even if, perchance, the business need would be better served by buying.

The thing is that such desire, such passion, is a good thing.  It will drive the creation of truly great and inspiring software when channeled appropriately.  It is positively good to be excited and passionate about your job, as that will translate into higher quality output.  It also is a matter of specialization--a developer can and should become a guru at his technologies because he needs to be the best at them to create the best implementation of a high-level, potentially technology-agnostic design.  It is unfortunate that some people devalue such enthusiasm rather than simply encouraging its proper application within a suitable role, namely that of a developer.