Too, in regions with winter weather (snow, or worse, sleet and ice), what few sidewalks or walking/biking trails which might exist are often further limited due to accumulated snow, if not slick with ice.

This can be found even within town/village centres, let alone the stroads and strip-malls on their peripheries. Walking and cycling become far more perilous.

Not impossible, but challenging, and a clear danger for the very young, elderly, or disabled.

Local ordinances to maintain clear sidewalks are quite often observed in the breach.

Then there's the shortened daylight hours, mentioned elsewhere in this thread.