Add me to the list of folks that used a Diners club, but wouldn’t carry one now, if it wasn’t a company issued/backed card.
I used it for travel (airline/car rental), hotels, and some meals. It had a generous “grace period” (60 days before late payments, from time of purchase, were charged), and as I was on 100% travel, I didn’t want to tie up my personal card’s credit availability.
They did also screw me on the rewards points I had accumulated when I closed the account (actually, my employer closed it), by saying I had 90 days to use them, but canceled them immediately.
It was sometimes, however, hard to use in non-business-travel focused restaurants/areas. Somewhat on par with how the Discover card was in the 80s-90s.