From an organizational and customer service perspective, it is silly for Boots and others to insist on things that are good for them. Annoying your customer into shopping with you is a silly and ignorant way to approach business.
On the other hand, in the UK, there are certain classes of medication that are by law required to be kept behind the counter. Boots isn't doing this because they have some internal policy, but because law requires it.
In the States, either there are thing perscribed or over the counter. There isn't this "middle ground" of Drugs, and there are not huge groups of people dying because someone didn't ask them questions on their screens.