if it wasn't for the free games i would not be using their store.
most of them are just in my library and i have never touched them,either because they don't run on my shitty non-gaming laptop or because i don't even like them(you never know,maybe some day my tastes will change)
Epic games have been giving a different free game every week for months. The point is not to promote those games but to give people a reason to use epic instead of steam. Once people build a library on Epic they are more likely to use it on a daily basis and more likely to buy games there.