Different .doc file formats

I'm asking this in the MS Office section because it's about MS Word which comes with MS Office & figured might get better insight into what is happening.

I was playing around with Word 2002 and MS Works 7 which both came with a MS Works Suite. Somewhere I read that Works .wps files were larger than .doc files. But here’s what I found.

I started with a Works .wps file & it was 13 KB.

Cut & pasted into Word 2002 & saved it as a default .doc file it now became 25 KB.

However if I left it in Works & saved it as a .doc file it was only 4KB.

Why the big difference between a Word 2002 .doc and a Works .doc file size?

My guess is that Word, being a bigger and more complex program, is adding more stuff to the file than Works is.