1) Heck, you can BUY your own submarine, if you want.
2) Remember balloons and other lighter than air vehicles? They were not dependent on oil, and yes some were practical and would still be, if oil hadn't been discovered.
3) I care, in fact, lots of people care. Going to space is much harder than flying or sailing, yet it took us thousands of years to develop proper ships, thousands more to develop lighter and then heavier than air vehicles, but because we didn't conquer space in 50 years we have to give it up? No, I don't think so. There's still plenty of time to conquer space.
4) They said the same thing about oceans...too big to cross, only insane people think they can sail across one, too many monsters awaiting fragile ships, yadda, yadda. Been there, done that, next argument? Millions have died on the oceans (and people continue to die on them every year), yet here we are, still cruising about with boatloads of tourists, shipping tens of thousands of containers on cargo ships, moving oil and natural gas about the world, on those big ol' empty oceans...
5) Not sure what your worries about death and life extension have to do with commercial space travel, but if you're that afraid of dying, a) I have bad news: so far, despite numerous attempts and lots of money/power/influence, no one has escaped death, not even Christ; b)I have good news: You can have everlasting life, if you're willing to accept Christ as your lord and savior.