The oceans are very hostile to humans too, really not much less than space, and a lot of ocean-going vessels are rusty hulks.
The real problem are the storms, as a naked human you won't survive in an ocean storm any longer than in vacuum.
At least you are going to space in a sophisticated vessel full of redundant life support systems. People sailed the high seas in old, barely seaworthy wooden ships dangerously overloaded with cargo, which didn't even have a reliable way of determining where precisely they were, because no one could tell longitude at sea before the mid-1700s or so.
Until today, some jobs at sea are pretty dangerous. Being a fisherman in Alaskan waters is much more risky than being an (American, not Russian) soldier.
People still do it. Which convinces me that people will risk their lives going to Mars, and more than a few of them. Some people are just built that way.
Generations of explorers, many of whom lost their lives for no gain, indicate otherwise.
Let us make a thought experiment. Let's say that Musk, tomorrow, declares "we are now creating a list of future Mars colonists, reasonably healthy individuals under 70 can apply from anywhere in the world, please send us your resumes".
Would they get fewer than 10 million applicants? I'd rather guess 50 million or so. Of course, some of those are going to get cold feet the moment they receive their one-way flight ticket in mail, but quite a few won't.
By your hypothesis, there would be approximately zero applicants. I don't believe that.
Sure they do. There’s a queue at the top of Mount Everest despite regular deaths; a couple rich folk got squished to pulp in the Titanic submarine last year. The free solo guy climbs Yosemite for the fun of it.
Plenty of people still have that itch.
Now it’s a race every few years - Vendee Globe. Something like half do not finish.