Consider for a moment how many URI's you know off the top of your head that aren't in Alexa's top 100. The goal of DNS is to allow humans to access web resources without search.
gTLDs will drive down search traffic for websites (I won't have to use Google to find redshirts.book), but most discovery today is aimed at individual pages, for which a URL shortener is still the best option.
It's also worth noting that especially with IPv6, gTLDs will provide much more convenient device specific URLs (chrisnicholson.iphone, for example). You'd have to be a math major to memorize IPv6 addresses.