SQL Server Browser disabled - why only Windows logins and users are visible?

I accessed a SQL Server instance using Management Studio by typing the computer name in the server name field. After logging in I couldn't see any SQL logins and users on the instance. Only domain users/logins were visible.

When I connected again to this instance using its IP address I could see all logins and users in the Security tab.

There is only 1 SQL server instance on this server (MSSQLSERVER) and the SQL Server Browser is disabled.

Why does it work this way?