I've also heard landlords say garbage disposals are a net-negative for maintenance visits: disposal-related problems are more costly than the occasional clog because someone put down something the disposal would've stopped.
Also, in multi-tenant buildings, disposals can be a nightmare. Too many people with varying folk wisdom of what's good to put down it. Some people create blockages for the entire stack or more, which ends up causing powered backflows of nasty wastewater into some units. And then what eventually gets snaked out of the drain, and dragged across their kitchens... mere bleach will never get that sufficiently clean. (Even after 3 of these kitchen-apocalypse episodes, you just can't get some people to understand that they can't keep grinding orange peels in their disposal to freshen the air, even when the rot of previous orange peels in the increasing blockage they created might be the reason they want to freshen the air now.)
I try to tell people that pretty much only water and dish soap should go down the drain, and that one of those few-dollar mesh drain strainers is a great tool to help follow this rule. (Also, a container for collecting most of the grease/oil that would otherwise go down the drain.)