In my opinion, it's because faith means so many different things to so many different people. Education, social standing, being poor, rich, middle income, destitute, Mental health, social and political views etc can be and are a factor in how people interpret faith. I don't think that there is anything wrong with that, most people that i know who do have faith are quite liberal people. If i went to another part of the world that may be different, although i would've thought that there would be a whole host of reasons for that.
In my opinion, religious institutions are like most things that have way too much power, and it's the people at the top who need scrutinizing and criticism. The huge group of people below them (us) have no power, yet it seems to me that they take the brunt of criticism from people who are opposed to religion. for me, that doesn't sit too well