«I'm aware that Outlook Exchange creates a .ost data file on both the mail server and on the local PC. And I'm seeing a lot of people writing comments on forums saying that you don't have to backup a .OST file because you already have it in the mail server. But that's because they have their own mail server available to them, right?»
Not exactly correct. The .OST file does not get created on the mail server end at all, they only get created on the client end when you use Outlook to connect to an Exchange server.
An .ost file is basically an offline copy of a mailbox hosted on an Exchange server. When you delete this file, it gets rebuilt automatically by re-downloading the content from the Exchange server as that's where your emails are stored. You don't need to back up this file at all as long as your Hosted Exchange provider is doing their job properly and backing up your emails.
Now there are third-party tools out there which can convert a .OST file to a .PST file format but these are generally used for recovery purposes should say the Exchange server blow up and you have no backups whatsoever.
There is no need for concern if you lose your .OST file due to a computer meltdown, corruption, etc. It will get rebuilt automatically when you set up a new Outlook profile or connect from another machine.
I hope this clears things up for you. You can still visit this forum and read there the recommendations on this problem