~~Most~~ many file types are just a renamed .zip

Or a renamed txt. Eg, .js, .py, .css, .html, .json

Thank God they went with file name extensions so we didn't have to preface every source .txt file with header content to instruct the editor about what kind of content it would have.
- <!DOCTYPE JAVASCRIPT>
- Why do I need to put that at the start of bash, desktop, and html files then?

AKA “Why zip doesn’t compress things much any more”.

I see images, audio, or video files distributed in zips far too often. You're getting maybe a percent of compression if you're lucky; just distribute the raw files or use a non-compressed bundle format like tar.
- But then,
?
- Zipping a file repeatedly typically doesn’t reduce the size further after the first time.
- Not sure what the original point was but curiously I happened to use file on a an Apple .numbers file recently and found that it was a .zip file in disguise with zero compression.
  
  So maybe the point was that it’s used often as a container format more often than it’s used for compression? Just my (unrelated) general computer work would also suggest this.
My 1.5gb log folders disagrees. But I never tried opening a .txt in 7-zip.

Your MOM is a renamed zip!

And if not, wow, she really kept herself in shape. Very good.

She keeping them filled tight if you know what I mean

Counterpoint: what?

Not really. The "file types" you're talking about are expected to contain whatever things in a very specific format.

You're really just saying "many file types use an efficient and common compression algorithm". Which is correct, obvious, and to be expected.

A .docx is just a zip file with xml documents in it.
- What happens if I put an mp3 or an epub file in there with the xml? Is it still a word document?

I don't get it... I must be missing something about zipped files.

You're not missing much. A few modern file types are zips with expected folder structures, especially MSOffice files. But this is nowhere near universally true.

You can open a file in your text editor of choice and if you see it start with PK (for Phil Katz the creator of the format and the original PKZIP/PKUNZIP programs) then it's probably a zip.

Also, by the logic of the OP, all DLLs are EXEs.
OP refers to the fact that you can rename some filetypes to .zip and unpack them.

Notable examples microsoft office files (.docx) or android apps (.apk).

Counterexample are media files (mp3, mp4, jpg).
- Notably, java jar files as well.
- OP refers to the fact that you can rename some filetypes to .zip and unpack them.
  
  So... you mean the zip program just rename them back? Why?
There are basically two types of files. Text files and binary files.

Most information are stored in text files so humans can easily understand it, and it's easier to find errors, review, parse. But text storage takes more space than binary files. And many complicated softwares normally need multiple text files or data files, many of them just store them together as a zip file so that it's easier to handle. Examples are .docx,.pptx, etc files in MS Office, try unzipping them and see what they contain. Zipping also has advantages of reducing file sizes.
Take a .docx file, using 7-zip, exctract it.

You will get an entire folder structure with several files inside the .docx file.

What OP means is that several programs use a zip file as a container for all the stuff they need in a save file.

The file extention is just a name for the OS to find the proper program to open the file.
OK, thanks for all the answers. I get it, a "docx" is a zip archive expected to contain something specific making it a docx. But why "most" though?
- I think 'most' is hyperbole for dramatic effect / increased engagement. "more files than you might think are actually following the zip file structure" isn't as punchy.

Most many file types are just a renamed .zip