many things in life and beer are not necessary but what fun would that be. As for flak, without that there would be a lot less posts on these forums.
Now in all seriousness, ale yeast have temperature ranges they like to hangout in just like we do. lower the temps and see less of them and of us.
Also yeast are only one part of the equation for clear beer. Variables, variables, so many variables. can anyone name some more of the variables for clear beer?