That exists and it's called ocean freight. Air freight is where you pay a premium to get a small amount of stuff there NOW. Ocean freight is what you use when

That exists and it's called ocean freight. Air freight is where you pay a premium to get a small amount of stuff there NOW. Ocean freight is what you use when you need 15 shipping containers of stuff there in a couple of weeks. Whether there is any market for an "in between" mode is an open question, and it's the business case of these airships for better or worse.