They are. Org format is kind of a better and more powerful Markdown. As plaintext, it looks cleaner to me.
The thing is, Org format is defined by the way Org-mode in Emacs handles it. Beyond Markdown-like features (which are rather easy to parse out; the format is similar), you get things in the data format that to date are handled only by Emacs. Think of Emacs + org mode as a better Jupyter notebooks than just editor for static text documents.
Consider this note I have in my org file for work tasks.
** DONE [#A] Testing prior to syncup meeting :CUSTOMER_development:
CLOSED: [2018-07-13 Fri 14:04]
:LOGBOOK:
CLOCK: [2018-07-13 Fri 12:14]--[2018-07-13 Fri 14:04] => 1:50
:END:
- [X] Baseline test for REDACTED
- REDACTED NOTE
- [X] Baseline test for SOMETHING ELSE
If you rendered this as a static document (e.g. export to HTML), you'd see the headline "Testing prior to syncup meeting", and the bullet-point list at the bottom. The remaining things are
metadata, nicely formatted by Emacs (and partially hidden; e.g. :LOGBOOK: / :END: block starts folded by default). The metadata shown are part of Org-mode's task management aspect - the todo state (DONE), date of task's finalization, time clocking (CLOCK: entries), tags (CUSTOMER_development). Together, they enable me to very efficiently mange tasks, track spent time, and autogenerate invoice data.
In this sense, org format is both a nice Markdown alternative, and - when coupled with Emacs - enables very powerful interactive documents that can handle task management, time clocking, literate programming, spreadsheeting, and other tasks.
I suspect Org will never be as popular as Markdown simply because, if you wanted to go beyond Markdown feature parity, you'd have to reimplement half of Emacs to handle those "advanced" aspects.