I use scooters rather than a WC so my solutions won't apply to all. I find the handlebars extremely useful for carrying things. For example, on my Sundancer scooter I can put $100 worth of groceries mostly hanging from the bars in plastic grocery bags. Overflow goes on the deck and in my basket.
When I take my dog out for a run with my larger outdoor scooter, I sometimes slide the handle of my dog's retractable leash onto one of the bars . When I'm off on a nature hike I hang a small backpack from one of the bars with binoculars, camera and lunch.
I hope the current fad for the D-handles on scooters, so prevalent at the present time, disappears before I have to replace one. I rented one and find them clumsy to drive. The D-handles fill much of the space in front of you, the pull-style throttles are more awkward than the simple push levers on the regular steering bars but, worst of all, they won't let me carry a thing using the bars.