As there would be if you worship money or communism or any other belief that is not a religion also for which wars or oppression has been caused.
The desire for wealth is one of the main things that makes it "somewhat less". But I think your "leave a void, someone will fill it" framing is too simple. Big religions don't block much greed, they overlap. So the increase in greed from knocking out religion would not be very much. Because of that and other overlap, the void is a lot smaller than the size of the religions that would be disappearing.