I've spent the last several years working with this scale of robot at my start-up. The practical use is mobile phone, tablet, and general touchscreen testing. In some products, such as automotive head unit displays or any medical device with a touchscreen, there are legal and company policy rules requiring that functional testing of a device must match human actions as closely as possible. Which means you can't only test the device through USB or some other back-end developer interface. In other cases, performance/latency testing teams want to test a touchscreen device as a black box, meaning with no extra instrumentation running on the device-under-test, to get good real world performance data. In all these cases that means a capacitive tablet stylus, instead of a pen, is attached to the end of a robot like Cartesio.

Huh, that's really interesting to learn. I'll file it in my big file of "Never thought about it, but makes sense"

(sorry, nothing otherwise constructive in this comment)

I just spent a day upgrading my printer and playing with Gcode, but it wasn't until your comment that I realized just how easily I can write a program that outputs gcode itself and add a pen so I can have the printer draw on paper. I'm going to have to test this right now.