Hi Catgirlseraid,

Nice to virtually meet you.

The crossings I've been cleaning up, are (almost always) where driveways cross "sidewalks."
Where the right of way clearly favours pedestrians, and being tagged as a pedestrian crossing tag adds a maintenance burden, but no useful extra information for users.

A pedestrian crossing is used to bridge a roadway between two adjacent sidewalks.
Where a sidewalk terminates, and a pedestrian crossing crosses a road/street to join another sidewalk.  
Where the primary users of the roadway, are vehicles that have the right of way.
Or to show a safe place to cross the road that may have added safety features, such as signage or crossing signals.

When using navigation in apps, (depending on your config) approaching a crossing may trigger an audible alert to warn the user.  This is a desirable behaviour.
Excessive alerts are undesirable, and users will quickly find the excessive alerts annoying, and disable the feature.  (When everything is urgent.  Nothing is urgent!)
To take the extreme view, there are 1.9 million residential buildings in NZ.  If each of their driveways were mapped and marked as pedestrian crossings, there would be an extra 1.9 million crossings/alerts to maintain.

As every driver (should!) know, If they're ever driving over a curb/sidewalk, they have to give way to pedestrians.  There's no need to map some driveways/sidewalks as crossings.
I believe an earlier version of some editing software defaulted to this, but has now been corrected in later versions to just join the two features together.

Some of the driveways should probably have been modelled as service roads, and I have changed a few of these where I believe that's a better fit.

Does that make sense?