> Elon has said that his motivation is to make humanity a multi planetary species thereby lowering the risk of extinction (asteroid impact, nuclear war, pandemic, biological warfare, catastrophic climate change, what have you).

None of those will leave the Earth even a millionth as inhospitable to life as Mars already is - so this motivation makes no logical sense.

Not to mention, with anything resembling current technology, any Mars colony will be highly dependent on Earth for a good few hundred years - there is no way to bootstrap a fully functioning high tech economy any quicker than that, and life on Mars would depend critically on the highest of high-tech (there is no way to live on Mars without computers, for example - so you would need to be able to build, supply and man advanced chip fabs on Mars before you could have a self-sufficient colony).

It also can't be forgotten that there is no proof that a human population can survive on Mars at all, given our current technology. For example, we have no way of knowing yet if humans could successfully reproduce and bear children healthy enough to reproduce themselves in such a low-G environment. We may require genetic engineering to actually be able to live on Mars (or at least human settlements might require huge centrifuges of some kind simulating high-G, which is way beyond our current abilities to do on a planet, or at least increases the costs thousand-fold).

If no one ever starts working on it, it will never be possible. Anything we can do beyond what our bodies allow on their own, someone had to work on.

Building 1000 rockets is not going to solve this problem though; and there are far easier experiments that can be done on mammals in low-G settings before "starting a colony" on Mars.

Not to mention, there are good reasons why the ancient Egyptians did not start work on a rocket program, even though they did want to fly.

Modern computer hardware doesn’t bring us the internet, among other technology advance, but for sure if nobody was working on it in the 1950s, 1960s there wouldn’t be the Internet we all so rely on today. Starships, a lot of them, are prerequisite if we want to have any significant presence in another planet.

> there are good reasons why the ancient Egyptians did not start work on a rocket program.

They didn’t have the required knowledge to do so. The rocket equation, after all, was only established a hundred years ago.

The problem of going to Mars is more or less solved. Advancing on the rocket front is not going to bring us one iota closer to knowing if humans can mate in very low gravity.

Also, computers are useful even if we didn't think of the Internet. 1000 space ships on their way to Mars are not very useful if we can't actually live on Mars.