Because Klopp isn't tactically flexible and will attack even when he doesn't have a decent defence. A more pragmatic manager would look at that woeful defence and say "ok, we need to be a little cautious when playing the likes of Spurs and City away".
But Klopp will have none of that! Atatck attack attack! End result is the occasional bruising. Still can't belive he spent nearly 100m on atatck this summer and less that 15m on defence.