WinRAR can _create_ RAR files. In fact it's one of the only pieces of software that can. The decompression algo is free, so it's implemented in 7zip. compressing files in the format is what they want you to pay for.
Uploaders who just transfer scene releases without bothering to extract will of course stick to RAR, but there's a lot of content these days that isn't from scene groups.
which are?..
If you need the interop then you can't beat ZIP
If you need a built-in recovery record (and find a working decompressing program 10-20 years later) then you can't beat RAR
If your corporate is insane and forbids 7z because it's FOSS/made by Russian then you can't beat RAR
Which are those 'better options'?
Is the algorithm itself actually available somewhere? IIRC 7zip had compatibility issues with some RAR files out there that opens up just fine with WinRAR, so I assumed they had to figure out the algo themselves.
https://www.rarlab.com/rar_add.htm
The source has the following restriction:
UnRAR source code may be used in any software to handle
RAR archives without limitations free of charge, but cannot be
used to develop RAR (WinRAR) compatible archiver and to
re-create RAR compression algorithm, which is proprietary.
Distribution of modified UnRAR source code in separate form
or as a part of other software is permitted, provided that
full text of this paragraph, starting from "UnRAR source code"
words, is included in license, or in documentation if license
is not available, and in source code comments of resulting package.