I completely agree with you 100% on this.
What's so special about the 7-Zip and RAR archive formats that some people would prefer to use them over the ordinary yet universal ZIP format?
It just needlessly complicates the sharing and extraction of patches through the use of different standards!
Zip achieves far worse ratios than rar and 7zip, 7zip in particular also has the ability to scan across files in an archive and use that in its compression database (7zip three of the same ROM and it is as though one ROM was compressed, compared to zip which goes filewise). 7zip has saved me many a time when I have had to email a variety of things to people.
7zip is also free and the first thing a lot of people replace the inbuilt awful Windows compression options with (said compression options traditionally have not handled rar or 7zip either). Those that don't do 7zip will probably go for winrar ( https://knowyourmeme.com/photos/426861-winrar
) as it was around before and in some ways won the compression format wars of the 90s and early 2000s. Because I am a bastard I am also duty bound to mention winace in all this.
For most purposes as far as patch making goes then I would agree a zip file containing the patch(es), release notes, possibly a program if you are going that way and the usual other bits and pieces will probably do. Most newer formats like xdelta will have their own compression options inbuilt.