I don't know anything about Chrome extensions but I know that typical bookmarklets function in all browsers. So my question is: why? Why not just using bookmarklet as is?

Naive guess—Chrome extensions run automatically on specific domains. Bookmarklets run only when clicked.

Some people hate having a bookmarks bar visible or just want to make more space for other things.

You can also get extra exposure through the chrome web store. It's not a lot, but every bit matters.

Brilliant! thanks. I've been planning on converting some of my markdown bookmarklets for blogging (http://5typos.net/post/259552063/bookmarklets-for-text-manip...) for some time, but was too lazy to checkout the specs. No excuse now.

I've always been annoyed in Firefox and now apparently Chrome that you cannot just have a simple, single-file extension if you don't need any external files.

Why can't it just regex the manifest, etc. from the extension header in a comment field.

Does something like this exist for Safari or Firefox?