Infatuation is literally neurologically based, in your medulla, or most primitive part of your brain. It is evolutionarily functional in bringing males and females together in the context of intense sexual attraction towards pair bonding (paired at least as long as it takes to insure the survival of the infant).
This neurological effect, that lasts between about two and three months only, is experienced by most as very pleasant. In fact, many folks become addicted to it and stay in relationships only until the effect wears off, which it must, as it is time limited. You cannot even work at getting it back, because it requires a new stimulus (attractive person) to re-ignite.
Love, on the other hand, is a choice that goes way beyond the neurological infatuation effect. When humans were far less evolved, they would likely move on to other matings to perpetuate the species. When brains got bigger, and language and culture developed, the stronger attachment of love helped to organize culture and communities, also serving a function of mutual safety and comfort.
Since love is far more long lasting and salient, the only role of infatuation is to lead to love.