Why would you not filter?
Because I've been using unfiltered gear for a number of years and never had a problem. Also, because filtering with a .22 takes a long while and the solvents can eat up the membrane.
Also, I don't sell... So, it's either for myself or close friends who trust the non-filtering method.
I've also been told by someone with a PhD in bio-chemistry that it's ok if you autoclave/pressure cook it.
So, there.