I think it's an entirely personal thing. It depends on what you aspire to and whether you can get anywhere close to it and it depends on what you think of other people's achievements.
Someone who finds enough purpose in life to be happy isn't going to care whether you think their life is valuable. Unless you become psychotic and try to kill them. Your opinion on their worth probably won't affect them unless you have power over them.
Alternatively, someone who you admire for having achieved something- a game designer, a musician, other people may utterly detest and think a complete waste of space. We all have different preferences in life. Different values we place on things.
If it's a case of, everything is worthless because nothing lasts forever. Potentially, everything could be destroyed I suppose in the end. Again, that's a legitimate view I guess. I think more people just try and live in the moment though.
If we followed that train of thought and didn't bother to try and do anything in life because- what's the point? We'd still be cave dwellers I imagine. Think of all the things you would have missed out on- games, music, films, books.
It's not a practical way to live for people. Most people need to earn their crust of bread. Then, it becomes finding the lesser of the evils I think. We use things like 'purpose' to motivate us towards things we enjoy doing. So hopefully, we can pursue careers in it or, at the least, do it as a hobby.
I know it isn't exactly a luxury because, welfare is required but, most people likely just don't have the time to question what they're doing. Whether it's worth doing what they're doing. If their choice is do nothing and starve, they'll likely work so they can eat!
