Open lobbies are smaller cause they don’t run on dedicated severs.People do realise that online servers, are used for a lot more than just straight up racing, right? With that out of the way, could it be related that there are a lot more variables in a normal lobby compared to Sport Mode? For example, in a normal lobby, you had access to your garage, you could setup your car, the host could even change the track or the time of day mid lobby. Way more variables. While in Sport mode, it was just straight to the point. This is the main differences I see between both types of lobby, and might be the reason why normal lobbies are smaller.