Do people keep eating those or is it a some sort of bridge/stepping stone to become having fully plant-based diet?
Some people prefer not to be reminded of animals at all, and they'll adopt a diet that doesn't resemble them. They don't need a "stepping stone" to it, though sometimes they could use some assistance learning how to eat a nutritionally complete diet. It's perfectly possible; it just requires a bit more thought.
It's not clear that these products actually are better for your health or the environment, but it's quite clear that they do reduce animal suffering. For many, that's sufficient.
Once you can properly season your tofu, sietan etc... the imitation meats kind of just become a novelty.