Officially, the end of riding tailboards and having open cabs died in 1992.
The National Fire Protection Association (NFPA), an organization that writes standards for the fire service (and building trades), has amongst their documents a standard called NFPA 1901, Standard for Automotive Fire Apparatus. NFPA 1901 tells you, and the fire engine manufacturers, everything you must do to build a fire engine. It gets revised every four to five years, and gives you requirements for major components like the strength of the chassis and how the pump will be built (if so equipped), and down to small stuff like the color of the webbing on a seat belt and the coefficient of friction for horizontal walking surfaces.
The 1992 edition of NFPA 1901 called for fully enclosed cabs, no more new trucks could built with full-open cabs or open jump seats (the rear facing “back” seats in a fire engine). If you already had a truck with an open cab or open jump seats, you could continue to use them, but no new trucks would be built with open seating positions. The 1992 edition also called, if I remember right, for all riders to be seated and belted any time the vehicle was in motion. That got rid of tail board (the back step) and running board (side steps) riding positions. No standing in jump seats, either. The requirements have gotten more stringent in recent editions, including a requirement in the 2009 edition that helmets cannot be worn while seated and belted, as the head protection in a seat cannot take into account both helmeted and un-helmeted firefighters. There are also data recorders for recording significant events, ie, vehicle accidents. Lots of new technology, but it also increases the price of the truck.
When we stopped riding on the tailboards in 1992, we had straps hanging from the grab handle above the hose bed that you would put around your torso, just under your arms. In theory, it would stop you from falling off of the back of the truck. It was still a scary ride, I only got to do it once before we stopped the tailboard riding. The old-timers will talk about hitting some of the hills in our town at high speeds and having all three of the guys on the tailboard’s feet come off of the deck, and that was without the “safety” straps. It was also warmer and less windy on the tailboard than in the open jumpseats. The wind seemed to go around you on the tailboard, the cab roof over the jumpseats seemed to redirect the wind into your face. There were some pretty horrendous accidents involving tailboards throughout the industry - it really isn’t a good place to ride.
There were a couple of purposes of open cabs. One was to allow communication between the driver and officer with the rest of the crew - you just had to turn around and yell. The other big reason was with aerials - you could see the incident much better when you pulled up and position the truck much easier not having a roof over your head. Some departments had canvas roofs or tarps that they could throw over the cab if there was a risk of the inside getting flooded. Most of the time you just wiped the water off of the vinyl seat and drove back. There isn’t much fancy stuff in an old fire engine. Heck, most didn’t even have radios until the 1950’s or later.
I still wish we were using horses and steam power. The job was so much simpler back then.