It gets to the point where it ceases to be "pretending". It may start out as a technique to get others to buy into your little experiment [1], but if you practice your pitch enough that it resonates emotionally with other people, and you practice your delivery enough that it sounds authentic, then eventually you will end up actually having passion for the product. Cognitive dissonance won't let you do otherwise; it's very hard to pretend to hold an emotion, over and over again, without actually holding that emotion.

Brand loyalty, religion, patriotism, hiring/onboarding, romantic relationships, and therapy are all other systems that work according to this principle. So is the expression "fake it till you make it" - at some point, you cease to be faking it.

[1] "Vision" is another term that's like this. Most (successful) entrepreneurs don't start their companies with a grand vision of what they want to accomplish. Rather, they start with a tiny need that tickles them. And then as they continue working on it, the need gets more distinct, they need to enlist more people to help, and eventually this tiny feeling gets massaged into a very big, very concrete vision that's effective at getting people to buy in.