When your staff grows over 20/25, the systems that have so far enabled you to move forward are just not good enough anymore. You cannot manage everyone anymore and you cannot give attention to what matters: your people.
If you do not run your now substantial business effectively, you will have 20/25 loose canons on your staff. Issues will grow but will not be dealt with properly.
Now is the time to get a proper communication system in place and to introduce a management structure as everyone cannot be in the same loop anymore . This means progress now has to be deliberate and not knee-jerk. A company culture is now growing and you must ensure you control it so that it does not degenerate into cynicism and bad morale.
You need to know what is going on, al the time. This requires your people to be part of the solution. This means that some of your key people will become managers, and if they do not know how to manage, you have a problem as they are those who will make your 25+ company a success, or not.
So you need to train them, retain them and ensure that the whole HR thing actually supports your business. Your product/ service is sorted. Your leadership is sorted. Now you need management muscle, this is a problem for HR. Make it up as you go along at your peril.
Over 20/25? It is time to understand that staffing is a strategic issue.