I recognize that there is an associated transitory cost, like the extra disk space and bandwidth used, but, again, such costs are inherent in working in a quickly developing field of technology. HTML5 is new, still only a draft, and most browsers' support is adequate but not really "mature". Things are going to be changing with regard to HTML5 video, canvas, etc. now and in the future -- you may want to stick with Flash video or links to video files until HTML5 stabilizes further.
As stated, if you don't think it's worth your while to transcode to WebM, no one here is forcing you. You are totally free to keep everything H.264 and give Chrome users a Flash fallback.