"ERROR: PLEASE INSTALL METAMASK TO USE THE BUTTON."

WTF? Screw you dude.

Don't draw the button if I can't click it! Don't say I can do one thing then force me to do another. That is bait-and-switch.

This is along the same lines as videogames showing DLC content you haven't paid for in the exact same way as the game's regular content. It's an obnoxious ploy to get you to buy the DLC, and they get to remind you of that fact every time you click it.