Bio-Balls are they needed or not

Thanks for the replies guys
I've been keeping both fresh and salt water aquariums for 30 years so I've got a handle on that nitrogen cycle thing
I think I'll keep the balls in, the sump I have has 3 lift out trays with each one having 4 large compartments - easily accessed and easy to give the balls a gentle rinse with saved water from a water change and only one tray to hold the 250-300 balls.
I guess my main query was that it only took the 6 or 7 years I was out of the hobby for we'd/dry systems to be replaced by bare sumps, wasn't quite sure why but anyway...