Maybe because colonizing Mars is a massive waste of resources that could be better spent fixing the planet we already live on? Or do you think the solution to scarcity is to have billionaires play with their space toys?
In my opinion colonizing Mars will begin to create a revolution in humanity in terms of resources, freedom, growth, and potential. I could get into why, but now isn't the place. The great thing is that capitalism enables people to decide for themselves what is likely to produce the greatest benefit and pursue that. Bill Gates seems to believe that solving malaria in Africa is going to be something that might help revolutionize society. And the great thing is that all of these actions are happening simultaneously, rather than mutually exclusively. And so indeed we'll get to see which efforts, if any, end up as tin cup telephones - and which end up as the next internet.
Right, you are making my point though, because you don't agree with how the money is spent. We have finite resources and infinite and different wishes. Capitalism tries to optimize between these.
Your view of how the government 'should' spend money is perhaps not mine, or my neighbours. Capitalism seems fairer and safer to me, than putting it all on government bureacracy.