Generally Protestantism is about Sola Scriptura and they have a huge abundance of material on this. Since this is the basis of most Protestantism this is the focus.
I have been to many, many Protestant bookstores\ also Pentacostal and non-denoms. If you are lucky the most you will find is a commentary about the early Church writings, or some books on Church history. I once ordered a Saint Augustine book at one, just for fun (I shouldn’t have done it as it was an inflammatory thing to do, but I was still studying Catholicism and a little punchy)
It is probably not any prejudice against the early fathers, it is just that if a bookstore is primarily catered to Protestants, then their focus will be on Protestant literature and of course this generally doesn’t include the Church Fathers. Or even look to a modern day Catholic like K, Keating, you will probably be told to check out the small Catholic section or be directed to the Catholic bookstore.
I haven’t noticed any trends in the way of excluding or including Church fathers in the general stock of bookstores, so maybe someone else could (name removed by moderator)ut on that.
Scylla