Pop culture at it's finest.
Better way of putting this; why don't startups write their web apps in x86 assembly?
Because not having problems in the first place is the sign of a 'good' programmer.
Good teams know when something needs less abstraction, to be sure. The same can also be said about the known knowns of what you are dealing with, and minimizing the risk involved with being ahead of the curve.
If using Backbone and/or Angular is not directly beneficial to the end user, I wouldn't recommend it on the projects I've worked on. That's not to say I would be against it; I just have found that in cases where I could have recommended it, it was for the benefit of the team instead.