It could be it just hooks up to the sewage directly but having access is nice in case you ever need to snake the weeping tiles. My sump pit has a drain in it so the water table overflow and weeping tiles just go into the drain. It's just a 1'x1' square cut out in the concrete and is about 1' deep (thickness of concrete). It could be the others have something like this and it's just covered with carpet or something?