Why are there so many files in /bin ? Why is /bin linked to /usr/bin?

That's actually not quite the right question. When I first noticed the phenomena, I found that there were over 4,000 files in /bin. My understanding was that /bin was supposed to be relatively small, just the minimal number of files (programs) that were required to run the system, especially scripts, but which did not require root privs to run.

However, in the process of investigating this problem, I discovered that /bin is actually a symlink to usr/bin.

Why?

My system is working properly, so I am reluctant to make any changes. My thinking is that this organization of file trees is not what I expected. There must be a reason for it. I'd like to know what that is.

Thank you.