No earthly reason? Any tool that allows a human to survive and do work on mars and the moon, allows them to survive in the earth’s harshest environments of cold, heat, environments without air.
Environments such as… most of the earth’s surface. Is this your first time on planet earth? Do you realise how much of the earth’s surface is desert, ocean and ice?
There’s a lot of real estate and a lot of mineral wealth out there too. There are millions of asteroids out there, and one of them (Psyche 16) is a 140 mile wide block of gold, platinum, iron, nickel. Robots might be able to mine it, but humans might be better at it. Robots have not fully replaced human mining even here on earth.
Another issue is that robots, while hardy, are not flexible enough to cope with the range of problems out there.
The physical reality of our universe is that light takes a finite amount of time to travel anywhere. You either solve the problem of human-level intelligence (very hard problem) and put einstein on a chip and send it, or you send dumb/mostly-dumb robots, and limit yourself to problems that can be solved with a 3 minute lag between sense,act,sense,act. Anything requiring real time skills, improvisation, reacting to unanticipated problems rapidly is out of the question with robotics.
Simply ‘carrying a weight up a slightly rocky hill’ or ‘descending a cliff with equipment’ is far, far, beyond the limits of robots on Mars currently. Carrying meaningful amounts of weight. Tying a knot to repair a broken cord, untangling a parachute, packing a parachute, building a shelter from weather conditions, improvising a cable as a rope, disconnecting and reconnecting cables and wiring. For a human, trivial. For current mars robots, hilariously impossible.
Looking at things (James Webb) is great, but we need to start doing things too.
There’s also the species survival question. This rock we’re on is doomed, one way or another, whether its tens, or billions, of years from now.
Anyway, if you don’t want humans to go, that’s fine. Vote accordingly and if you don’t like the result, migrate to a country where the tax money is spent as you like. Problem solved.
There’s no earthly benefit to sending humans to play sports, theater, music, performances, roles on TV, elderly care, school teaching either; they’re ephemeral, ‘pointless’ human experiences much like a mission to mars will be and we could replace the humans doing these tasks with robots and get a more consistent performance.
Oddly I never see people advocating to get rid of those sorts of things, even though the national budget for them is more than an order of magnitude larger.
This planet is about 0.00000000000000000000001 of all that’s out there to see and robots are a powerful but limited way of exploring it and a very limited way of interacting with it.
Besides, the entire budget of NASA including all these programs is 0.48% of the US budget.
If you care about costs and efficiency, I suggest you start advocating for the US to change to a rational healthcare model like the rest of the OECD has. You’ll get the same health and life expectancy outcomes, and the 5-10% of GDP you save will pay for 10-20 NASAs, we can devote a few of them for human exploration and a few of the others for robots and telescopes.