Having the words there as a kind of safety net can be helpful and even necessary. But that's not the same as reading a song, which can really get in the way of singing it, the same way that struggling to remember the words can get in the way.

It's really worth putting in the effort, as Lighthouse expressed it, "to go over lyrics periodically". Singing isn't primarily about making beautiful sounds, it's about stortytelling and picture painting.