Most aquarium plants flower, they just tend not to do so in a tank. The thought is most aquarium plants are marginal that sometimes grow unsubmerged and most of the time stick out above the water surface, which has to happen for the plant to make a flower.
When I initially bought my cabomba it was a few inches tall and was loaded with purple flowers. After planting, these flowers all fell off. My tank is 24" deep, and while my cabomba grows about a foot per week, it never flowers.