Its not a stupid question. In the wilds of the oceans, all life has adapted to gathering food from multiple sources. This is evident with corals where they not only use algae to produce their food but also have polyps to help capture food as well. In the wild, there are multiple forms and methods for our corals to gather food but in the reef tank, we limit the food sources due to the limited capacities we have in our tanks.
In my own tank I have a mixed reef with a large size fuge area and a lone orange sponge. When I stopped dosing my phyto mix, a combination of phyto, reef roids, reef eggs from reef nutrition and zoa food, I noticed that my sponge started to lose some of its body mass and the skeleton was starting to show. Once I started back up in my regimen, I noticed that my orange sponge not only grew back its lost flesh but I also noticed an increase in pod and shrimp growth in my fuge areas.
Long story short, dosing phyto offers yet another food source that many organisms in our tiny reefs can utilize and for some critters like pods, mysis, sponges, their primary type of food source. I'm even playing with the idea using a wine bottle and a dosing pump to dose the tank throughout the day. The Wine bottle keeps the phtyo nice and cool while it waits to be dosed into my tank.