Because I got sick of explaining why the diff lock button in your Cruiser / Discovery is not the same as the diff lock buttons in mine…..
https://web.archive.org/web/20060816054148/http://www.safari4x4.com.au/80scool/george_couyant/diffs/diffs.html
Summary: If you own an AWD car – AWD should stand for Any Wheel Drive – Any wheel with the least traction will get all the drive. The centre diff button just turns it into a “normal” “traditional” 4wd, that is one front and one rear must lose traction to stop going forward. This happens on many hills and is the reason pressing this button doesn’t do that much more to where you can go.