Isn't this the opposite of "pick the right tool for the job"? Building with whatever you're most comfortable seems to be a superficial reason. Different platforms/languages have real diversity in their strengths and weaknesses.
You raise a valid point if you're putting up a shelf. But if you're programming then you'll be at a disadvantage if you're not familiar with the tools at hand. Even a designer is going to suffer if they're made to use the Gimp when they're used to Photoshop, not because Gimp is or isn't a good tool but because the interaction is different.
Switching from Lightroom to Aperture I've noticed substantial differences in my photography, and I'm not a very good photographer. I'm considering switching back to Lightroom - I'm sure Aperture's great, but the learning curve is harder than switching from Vim to Emacs.