Swim Fins Helpfull or a Crutch?

I like to swim with fins some days, I have the zoomers and some regular fins. I notice when I swim finless that I feel slow as a snail.If I have been using the fins for a couple of days. I know some swimmers that only use fins as thats the only way they have been able to learn, to them I say great what ever works for exercise but have noted to them that they should at least be able to swim finless to get out of the pool for safety if they fell into water anywhere.