The more people you have the more processes you need. With 5 people the same person usually does the same things or they've seen the person who usually does it do it. So they do it in the same way, know the tricks or who to ask if it goes wrong. Your working environment is usually small, communication fluid, so people just know what goes on and how it works.

As you get larger you see what you're seeing - not everyone is in on the meetings, knowledge in one person's head isn't shared and people don't know who to ask.

I worked on a simple barcode database setup years ago. Originally it was just a spreadsheet one person 'owned'. Then I made it into a webapp that I and original owner could both add items to - enforcing unique entries and validating checksums (plus an API I could querry). More process, but still a lot was in our heads. When a 3rd person started using it, they added something in lower-case (we always wrote refs in caps) and a variety of case sensitive bugs were found. I had to fix the DB manually and started adding hints and validation.

The more people you have using something the more problems you will have and the less feasible it is to walk everyone through the system in person!

Documentation, make process, make efforts to share knowledge. No way around it.