@Laura2592
I think single nights work well for certain scenarios; listing near airports or rail stations, in-transit stops on major travel routes, high demand cities, gap filling in high season, events, sports or concert venues listings, retail or business place listings as an example.
If a host also wants to chase after cleaning fees to make a higher yield, that's a reason too.
Probably non novice hosts have an idea of what their sweet spot is in terms of their best minimum night and whats practical.
There are plenty reasons too, for not allowing one-night bookings as you rightly say.
Airbnb just recently updated the 'Performance' section for listings, but the provided metrics are useless for any host to make an informed decision on one night bookings without any provided analysis.