Am I the only one who still makes websites with very little JS in them? One jQuery thing here and there. Using Backbone would be overkill and to be honest I can't think of one hypothetical project where I would need it.
A lot of JS tends to be required when you're building a big, dynamic web application, or your website needs lots of modules and lovely little widgets. If you can avoid writing a lot of JS, then that's great - but HTML / CSS alone can't provide the features that a lot of users are expecting.