The disdain for casual hobbyists you show here implies that you are probably not the target audience for the article, which is targeted even lower than hobbyists: people who need an early introduction. Professionals have very different needs than hobbyists and therefore need different materials and suppliers.
Eh true. And it's not disdain, those companies are great for what they do. The guy above just implied they sucked, which isn't the case. They're great for their target market
I actually disagree with you completely. (And I'm a professional, this is my day job.) For breadboarding I buy from Adafruit and Sparkfun, since they have good selections of breakout boards, MSOP to DIP adapters, etc. DK and Mouser have plenty of that, and some really nice stuff (like TI's adapter "EVMs")... but for prototyping on a breadboard, I start with the other guys.
(Then usually tack them on to a Digi-Key or Mouser order, because if it doesn't require something weird, I probably didn't need to prototype it.)