I assumed the accidents were a dramatisation but the smells and brake downs must be somewhat common.

No? They're not anymore maintenance than a regular sink as far as that goes. They almost never break and they're not any worse off than a regular sink as far as cleaning goes.

Their rationel, from Wikipedia:

Food scraps range from 10% to 20% of household waste,[18] and are a problematic component of municipal waste, creating public health, sanitation and environmental problems at each step, beginning with internal storage and followed by truck-based collection. Burned in waste-to-energy facilities, the high water-content of food scraps means that their heating and burning consumes more energy than it generates; buried in landfills, food scraps decompose and generate methane gas, a greenhouse gas that contributes to climate change.[19]

The premise behind the proper use of a disposer is to effectively regard food scraps as liquid (averaging 70% water, like human waste), and use existing infrastructure (underground sewers and wastewater treatment plants) for its management. Modern wastewater plants are effective at processing organic solids into fertilizer products (known as biosolids), with advanced facilities also capturing methane for energy production.[20][21]