Maybe we need to change our attitude to buying certain things. If you use a bookstore as a library, then it's not a store, it's a service. Every so often you should pay for that service by buying a book. If you use the reviews on Amazon a lot, or use the wish list service to keep track of everything you need to read, then every so often you should buy from them.
You could also say that smaller local stores offer a service just by their existance, just by being convenient and offering you a choice. Every so often, you should buy from them. You shouldn't feel obliged to buy from every store you ever browse in. But when you cross that line of using them as a service, and wanting them to continue providing that service, you should be prepared to pay a little towards that.