The short answer is someone designed it specifically to demonstrate calibration across different printing conditions and it took off in no small part because it's cute and can serve as a filament sample.
I think it's because Benchy has a crazy amount of changing surfaces and is easily printable with or without supports, scales better, and doesn't take terribly long to print.
I bought a 3d printer in 2015 and it took me probably a month of screwing with it after work and on weekends to get to the point that I could make decent things with it. My brother bought one of these last year and was sending me pictures of shit he made the same day he started. I was was a bit jealous.
I’m really wanting to get a Bamboo Labs printer. I have an Ender and I honestly stopped using it because it took way longer to setup the printer than I spent printing. Whereas I believe Bamboo printers are in a state where it’s plug in and print.
I bought a Mini with AMS last month to add along side my old Mk3s+. It's faster, (though not that much faster in the end), and the AMS works very well. And it was easy to setup and get running.
But it has had some basic design issues that need attention, (for which there are community fixes you can find). And even after careful tuning, it really isn't any better than the Mk3s for print quality. It's just easier to print in color if you choose to be wasteful with filament. Like I am doing right now.
Coming from an Ender, it will be an upgrade though. I do think the the A1 series is a good inexpensive home use printer though.