We will sometimes purposefully lose a few if we have won all our attacks. We have level 70 and 80 members in guild and we don't want to go too high or else we lose every single battle the next week unless it's a battle with less than 20 towers.
So when we purposefully lose a couple battles it's so that we don't jump too high in the ratings. We can't compete in the top 25 and don't want to be in top 25 because it then means a week with no rewards. So we surrender a few on the weeks when we stand to jump too high so that we stay ranked where we realistically should be.
Hopefully that makes sense.