Guy Threepwood
Mighty Pirate
Only because, at that time, we didn't have the technology to send rovers. At least not like now. During that time, people were the most reliable forms of observation we had.
hmm- but probes started reaching the moon a decade before people- eventually taking good clear pictures and testing the surface, everything was pretty much already discovered about the moon before the vastly more expensive, risky, task of landing people- mostly for it's own sake yes?
Likewise today, unmanned craft can tell us everything we need to know about Mars, but we still desire, plan, a manned mission.
An illogical waste of money we could argue, with nothing new to be learned- why wouldn't aliens have the same illogical curiosity to experience Earth for themselves?