Largely it is a failure of financial instruments. No one has an Extreme High Risk, Very High Capital, low yield 10-15 year investment plan.
Projects like that have previously been undertaken by institutions like Governments and the Vatican.
The Government posting a $30 Billion dollar prize for the first private company to land people on Mars would probably be enough to close the business model. It would be a lot cheaper than $130 Billion Nasa currently plans to spend and would involve multiple teams.
As it stands private companies are having to take the loooong road to space. It literally has a 100 km high barrier to entry.