The web isn't very touch-friendly. I've used a Chromebook Pixel as my primary laptop for years, and I can say with authority that websites and web apps are designed for a mouse and keyboard. That makes sense, because for 20 years we've been using computers with a mouse and keyboard to surf the web. Change comes slow across an entire ecosystem like the Internet.
Things are slowly changing, with companies like Google and Apple making their front-end for online services more touch friendly. Today's modern smartphones and tablets make for a pretty good web experience even when we need to use our fingers to make things happen. But that's not the only reason why you'll want a touch screen on your next Chromebook.
Go back to September of 2014, when Google officially showed off a few Android apps that were running on Chrome OS. Some of us loved the idea of a Google Play store with apps that would run on both Android and Chrome. Some thought that Google was moving away from the original purpose of a Chromebook by filling it with apps you could install. Others didn't care one way or the other. But Google is Google, and they continued to push the idea forward and work on building an Android runtime for Chrome.
Snap back to spring of 2015, and it's clear that things are just about ready. Google has released the ARC Welder project (Android Runtime for Chrome) to the public, and all Android developers are able to package their apps for Chrome, and even put them in the Chrome store. And it works pretty well. It's easy to re-package just about any Android app for Chrome, and you can bet plenty of developers are playing with it.
When it happens — and it will happen — you'll be glad you have a touchscreen to do more with all those apps. Long-pressing, swiping and other gestures are pretty tough to tackle with a mouse, and while a trackpad can make things easier, touch-optimized is still touch optimized. We expect the web itself to become more and more touch-friendly over time, but adding Android apps to your laptop is a great reason to be sure you have a touch screen to best use them.