Would Amazon be possible without trucks? How about Walmart?
Not Walmart, but Amazon makes even more sense in a horse-driven economy: First, you don't have to ride to the store and back -- mailing a small item is much cheaper than that. Second, with the price of shipping per mile per pound being higher, there would be more of an incentive to ship items directly from the manufacturer to the consumer. Mail-order catalogs existed before the age of cars.
People crave financial stability. Bitcoin will not give it to them. I'm not averse to the idea of a distributed ledger acting as an underlying settlement mechanism for global finance, but Bitcoin does not achieve that goal either as it's zero sum (whereas economies are actually growing).