Why don't churches offer a roof for the night for unfortunate individuals?

They do. Many Christian charity organisations are established for the sole purpose of helping the destitute and the homeless, also battered wives/husbands, alcoholics, drug addicts and prisoners (both while in prison and after release), right here in Britain. Check out Bethany Homes on the Internet and see just how much this Christian group does in Scotland! And please stop thinking about churches as being buildings that only open for a few hours each week. You don't seem to have any idea what the church actually is, or that denomination has nothing to do with any of this.