What’s the deal with all of these people selling French Bulldogs?

I recently saw a sign in Sugar Land that advertised French Bulldogs and had an 832 phone number. Thanks to the City of Sugar Land, the sign was taken down within 24 hours. Now what is the deal with these people selling dogs? What's so great about French Bulldogs? Why the heck would someone buy a dog from a rando that advertises from a crap roadside sign? This is just all 100% pure crookedness.