Why use the command apt-get --purge remove over apt-get purge in Linux?

The command apt-get --purge remove has been around since APT was added to Debian and it used to be the only way to completely purge a package with apt. The command apt-get purge was finally added in the last few years, the old option was not removed, and there is still lots of documentation showing the older syntax. They do exactly the same thing.

I often still use the longer command apt-get --purge remove simply because I have used it more often, and forget that the shorter version is now available.

One other useful thing to keep in mind is that the --purge option can be used with the apt-get autoremove, and there is not equivalent apt-get autopurge. So if you use the apt-get autoremove option to remove automatically installed packages you will have lots of old crufty configs from those packages, since you just removed them.