Often, natural flowers like snapdragons, for example, are like puzzle boxes, where bees have to figure out how to open them, how to pry the petals apart, and how to manipulate the structure to extract the rewards.
And if you think about some flowers like snapdragons, where the bee actually has to open the flower and climb inside, having a very grippable flower can actually help.
So from the plant's point of view, if you think about something like a foxglove or a snapdragon, what the plant would like is the insect to go in the front, access the nectar and get dusted in pollen.