I’ve seen 'em and I’ve used them in the past. They’re a fine solution, but they still require cleaning and a couple of satchels of Taster’s Choice or whatever is easier on the KP and also much smaller than a giant coffee syringe. Showing up at the pay-for-pitch in the station wagon is one thing, but usually all my stuff needs to either fit in my panniers or my backback.
There are guys I’ve hiked with who have them, though. To each their own.