It is more likely that the owners wanted to recruit great talent, have someone whos mission is to create a nice everyday environment, help spot and train leadership or any other number of things that the HR professionals, I've had the pleasure of meeting in my career, are great at and care about.
Between large evil corporations and tiny lean teams, there are variety of companies where a HR professional can help you make it or break it.
Workers' unions can also be risky. They have their own agenda, leverage over management, and will encourage you to speak up often without considering your own best interests.
Recruiting (however and by whomever it's done) is essential to your company's ability to create products or services and generate revenue. This is what most people think of when they think about what success means, so it's not surprising that you would think of HR as key team members if you're accustomed to them doing recruiting. However, the other function, of protecting the company's owners from its employees, has nothing to do with the success of the company in that same sense; it doesn't help to generate revenue and may even hinder your progress toward it by separating the company from some of its most productive and creative employees. Instead, this function serves to direct as much of the revenue as possible to the owners of the company rather than employees (and/or their lawyers). Since most people who aren't the owners are focused primarily on products, services, and growing revenue, they don't think about this as being part of "success", so this traditional HR function makes them "the enemy" and an obstacle to success as they define it.
Both views of HR are correct; which is appropriate depends on who you are and on how your company assigns responsibility for recruiting. But make no mistake about it: if you're an employee, as the OP is, the part of the company that protects it from you is not your friend, even if the same people also help you recruit great teammates who help you achieve your goals.
In the US, many regulations kick in at 50 employees.
That said, HR is never your pal. Then again, the owner of the company that you drank with in the smaller days wasn't really your pal either.
True. The hiring of professional HR means the mask has finally come off. You can't pretend to be one big happy family anymore.
Job #1 of HR is to protect the company from its employees. The reason for hiring a HR professional (weirdly they never refer to themselves as "resources") is that the owners or managers now feel that they need that protection. There's a gulf now between management and workers, that perhaps was a narrow stream before. You've instinctively grasped this, that's where your apprehension comes from.