>>46516430They do not work on humans no. People have tried to use Pokeballs on humans (Green In Let's Go tried and failed). So no, it is however a cute gesture as like a "I choose You!" for proposals or invitations.
I 100% bet people use Love Balls for marriage proposals, putting the ring inside and all that jazz.
>>46516454Unless your wife/girlfriend/boyfriend/husband is a Pokemon who views Pokeballs as a sign of romantic commitment...yeah its not a romantic gesture.