Last I checked, Lewis & Clarke didn’t have the benefit of gas stations. Analogous statements could be made about Magellen, Columbus, et. al. Jefferson didn’t build a highway system – that was Eisenhower’s job. When it comes to space, we’re in the age of exploration.
Lewis and Clark didn’t start out on their epic expedition carrying all of the food and water they’d need for the entire trip. They took advantage of local resources along the way. In space, that’s a bit harder. Yes, there are resources on the moon and Mars that can be effectively harvested and put to good use. However, it’s irrational to assume that you must launch one really big rocket (because that’s the way Apollo did it!) carrying everything you need for the trip when there are much smarter and more cost effective ways to do it. Propellant depots is one of those ways.
