Like They Used To, Hamilton, Montana

Whilst trundling about my old neighborhood, what does my meandering eye espy? A 1950s-era International dump truck - still working hard, and looking for a new home. They really don’t make ‘em like they used to. 

 My ever-burning automotive question (please forgive the strong overtones of whine): whyever did they quit making those delightful little triangle vent windows as part of the front door? 
If you know such things, please enlighten via the comment field.