Product managers add features and/or speed up development by using more resource-hungry runtimes up to the point where the users still tolerate the performance but barely so. Once the product has enough traction and switching costs, the user would rather tolerate the mild pain of slowness than the more acute pain of switching and adapting to a (so far) faster competitor.

This is very much like the idea of the optimal price point where the customer already cringes but still buys.