While less of a consideration for established teams, it dramatically raises the barrier to entry for those who are learning as well as those who currently have much simpler requirements. Those are the future members of that established team. Adding hurdles to the process of learning will, in the long run, result in a smaller, more homogeneous pool of experienced developers to draw upon. It's a self-perpetuating cycle - making folks learn by using complex build scripts will result in experienced developers who then create further complexity because they've self-selected to be those who happen to think in that mode.

That's not intended to suggest that progress is bad. Rather that it's a bit short-sighted of us, as an industry, not to consider the ramifications of enforcing a workflow that happens to be trivial from the limited perspective of long time front end developers.

{ Edit to try to make the last paragraph sound less accusatory. Sorry! That wasn't my intention. }