Humans explore. It seems to be in our genetic make up. We went to the moon because we had never been off our planet. The amount of technology that traces it's way back to military and space exploration is massive. Just do a web search. Everything from GPS to scratch resistant glasses to bonding agents ....
Going to Mars is the next step. If we are ever going to leave our solar system we need to be able to travel and live in space for long durations. Far longer than anyone has lived on the ISS or Soyuz (438 days by Russian Valeri Polyakov). Mars is the closest planet to Earth that could be colonized.
Granted the space program has been wasteful in some ares but it seems the tighter budgets have done them good. There are unmanned probes going to Mars. The last rovers sent to Mars lasted far longer than their anticipated life span (IIRC one of them is still operational).
We were in a race to out do USSR....Sputnik sealed the fate of our space commitment.
Yeah and those probes are the early scouting for a manned visit. Just like the moon probes were.