"You must not delete the work of other contributors."

Oh dear. Oh dear, oh dear, oh dear.

I did NOT "delete" the work of other contributors. I replaced it with better tagging. To quote the wiki:

"The following closed ways should be treated as linear features:

* "barrier=*, for thicker hedges or walls or detailed mapping defined using an area add area=yes
* "highway=*, see 'Highway areas' below for more details"

Those highway=footway and area=yes tags have highway=footway lines within them. 

https://wiki.openstreetmap.org/wiki/Key:area:highway

That tagging which I correctly used is describing the shape of a pavement area. The linear highway=footway ways through the area tagged with area:highway are the ones used for routing.

The combination that you want to use occurs 456,857 times, whereas area:highway is used 349,749 times.

So get off your high horse and actually look at tagging use reality instead.