HR for startups wouldn't and shouldn't be like HR for big companies. It doesn't have to slow a company down at all, and it's definitely a function that can enhance a company culture in really positive ways without dampening it.

However, if you think sexual harassment doesn't happen in small startups, you're not paying attention. At the end of the day, HR is a mediator for the company to protect it from lawsuits. HR can stop a little issue from turning into a big, expensive issue, which is positive for both the company and employees.