Typical taxi speeds are less than 20 knots. These are speeds at which city-transport buses regularly operate & even exceed. Buses don't mandate seat belts & in fact even allow standees.
Now my question is: Is the risk of collision higher in a taxing aircraft? Are decelerations higher? Or do we operate in aviation with a lower risk appetite.
As a counterexample, during flight even if the seatbelt light is turned on, toilet-visits seem allowed (mostly, unless its severe turbulence). On the other hand, the ground taxi period seems an absolute PAX movement prohibition period akin to takeoff & landing.
Is ground-taxi riskier than in-flight seat-belts-on periods?
PS. Don't interpret this as advocacy to get rid the seat-belts during-taxi rule. Just curious about the differential risk assessment.
In any case most safety prohibitions are a risk-vs-convenience tradeoff. Just evaluating that tradeoff in this particular case.