If it's really 90% of the people who are left behind, it's probably not good for the company really.

People in existing teams will be very fatigued from getting to know new people and then trying to forget them. This is well documented in the military. After a while veterans don't want to get to know the fresh reinforcements that arrive into their unit, as the new guys will probably die quickly simply because they are inexperienced and thrown to battlefield. As a result, any investment in social relationship with them is wasted. And as a result, the whole unit will get grumpy.