I use (very small) recaps for several reasons.

One is to remind readers what was happening. They have other things in their lives to remember, and I don't want to ask them to go back and reread the other installments to get a handle on what's going on, especially if they're coming back to the story after a month or more. I don't need to retread the entire story, just enough to jog their memory.

Another is for fun. Recaps are their own kind of expression, and hopefully readers familiar with the story will smile at the way they're expressed. Eventually I want to even include hyperbolic, possibly inaccurate chapter previews. The recap is another of the writer's tools, one that is reminiscent of when this format was used before, and one that is hardly ever used in normal fiction now.

The last reason is for myself. With the recap at the top of the page I have better focus on the story I'm writing, and writing the recap helps me to pinpoint what the next chapter needs to have.

I don't mind if a story doesn't have recaps, though sometimes I have found myself scrolling through an old installment trying to match names to descriptions; it's just something I like doing.