You don't need them. But you can take some good pictures with them, if you know what you're doing. I have a couple, one for ocean water and another for fresh water. I like the realistic colors filters give. But you don't see many magazine pictures shot with filters.
Filters can be useful for specialty shots.
But they block a lot of light, so you have to use a really fast film. You may lose contrast and richness of detail. High-quality film is a must. Mike Engberson meets garibaldi. Nikonos V w 35 mm, red filter, available light using Kodak 800 Max film.