This topic was raised before.
IIRC, the answer from Mean was that this is due to a lack of time.
You can extract the files from the installer though using something like universal extractor.
Place these files in any folder you like and rename avidemux.exe to avidemux_portable.exe (constraining all application data to this folder).
Just a caveat - not done this lately myself, so hopefully this process still works.
The nightlies offer zipped versions of ADM - why not try these instead.