RTF? Surely there's no reason to resort to that over HTML anymore?
Is there a reason not to? To each his own, I suppose. I like to write things up with WordPad because it is very light-weight. I prefer to stay away from Word and FrontPage, which are the only programs I have that save HTML. RTF is old, but it ain't broke and it usually suits my needs.
As for the 20 meg RTF, I don't know what to tell you. I don't normally place pictures in RTF docs, but I wouldn't expect doing so to make an RTF stupid huge. It is entirely possible for the creator to do something silly that can bloat the file, but stupid is most certainly not restricted to the world of RTF.
The way I see it, WordPad/RTF is just NotePad/TXT with formatting. That's how I use it and it works great. HTML is fine too. TXT works. Just don't give me a PDF and we're cool.