The models in the "Frequent batch auctions as a market design response to HFT" paper by Budish et. al.; i linked the slides in another comment.

Since batch auctions use single-price clearing, market makers can post bids and asks without fear of being sniped (so its less risk, not more). And since you can't snipe, they have to compete on price rather than investing in faster connections, resulting in narrower spreads.