The need for the side columns to have a degree of strength is a bigger problem for visibility that the bulk added by side curtains.
Driving '60 and 70's cars was great for visibility due to the amount of glass and narrow pillars. The risk of dying in a relatively low speed accident was less ideal.
My girlfriend's 2006? Subaru Legacy had thinner columns than her 2013 model. Not sure by how much, but it was very noticeable at first and I still find I sometimes miss seeing things in the new car that I never had a problem with in the old one. Maybe they are wider now for strength and side air bags. In any case, maximizing cars for crash-test-dummy preservation may not minimize for human harm due to car accidents. With automatic cars this may be not be a very big problem, but they are still a ways off, I think.
