The steps and safety railings are a direct response to injuries in the mining industry caused by falls from machines. When an operator falls off a machine, and hurts themselves (sometimes enough to stop them from working again) .. company costs go up, as workers compensation has to paid, and insurance premiums go up.
In the old days, when a 130 HP D8 was a big tractor .. falls weren't a major problem (although, anyone who has slipped on wet shiny track shoes, and fallen a$$-up between the blade and tractor, knows, that it HURTS!) ..
However .. when the machines started becoming the huge size they are today (and you can be 4.5 to 5 metres - 14'-16' off the ground, when you're up on the operators deck) .. falling from that height, can even result in death, if you're unlucky enough to land on your head .
Once a serious injury results, Govt Safety Depts/OSHA start drafting more laws and recommendations, to try and prevent a repeat of the accident .. and so on it goes ..
http://www.docep.wa.gov.au/Resource...MP/Guidelines/MS_GMP_Guide_personalaccess.pdf
As a result, building ladder/steps on the big dozers and trucks, and putting rail guarding on the operator deck, makes sense. It's big business, now, designing up the best steps and rails, that will perform satisfactorily in an earthmoving environment.
http://www.powerstep.com.au/
99% of the step designs I've seen are retractable .. even the big trucks need retractable steps, just to reach the front bumper ..