Employees of companies that are not public but who are given stock options have no way to easily liquidate those options. This allows those employees to get so

Employees of companies that are not public but who are given stock options have no way to easily liquidate those options. This allows those employees to get some money NOW instead of hoping someday the company goes public or is bought out (which in most cases will never happen). For the buyer this allows them to get in even earlier. This is complicated of course by the fact they are not public companies and requires a lot of extra paperwork.