Speaking as an owner of the FunKey S (same internals, different form factor): yes, a big part is novelty. Pulling out a keychain-sized device that can play Metal Gear Solid is a hell of a party trick.

But that said, if you primarily play games on it that are designed for portables (Game Boy, Game Gear, Lynx, Neo Geo Pocket Color, etc.) and have halfway decent eyesight, it’s actually quite enjoyable. Games designed for a TV often have uncomfortable cropping or tiny text that gets eaten up by the ~256x256 resolution of the display. But pulling it out to play a little Shantae while waiting in a line is a delight.