Because you might die, waiting for failure rate to come down. Failure rate comes down, more people will try, causing failure rate to rise.

Yes, tha failure rate is high. Rewards, if you succeed, are also high. Your choice.

Because you feel like you have to. You will likely fail, but you are driven to try. Most fail, but sometimes the lottery ticket pays out.

Because you have an idea for a product/service that you think people will want/need enough that they'll pay for it?

Because you think you can create the product/service before you go bankrupt, and that you can then sell it for a price the market can bear that will allow you to make a profit?

It's not just a coin flip, which is the impression you get looking at statistics too much.

You may have a vision for creating a product or service that you believe requires starting a company, and you believe you have a compelling business model that will sustain the company. Failure may happen, but the drive for getting that product or service out there may overcome fears of failure.

The world may be a different place had Steve Wozniak decided to remain an engineer at Hewlett Packard's calculator division instead of creating a company to sell the computer he worked on as a side project, though it did take a lot of convincing from Steve Jobs.