Do you watch Seinfeld? Remember the episode where Kramer was going to establish a build-your-own-pizza parlor, where the customers would roll the dough, spread the sauce, add the cheese and toppings, and throw the whole mess into the oven?
Making your own ice cream is similar to making your own pizza. As an aice cream vendor, you'd not suffer a loss of business if your customers bught an ice cream machine.