[Tagging] Why are railway=crossing and level_crossing separate tags?

[Nathan Edgars II]

According to the wiki, railway=crossing is "a point where pedestrians 
may cross a railway", while railway=level_crossing is "where a road 
crosses a railway". But footways are also represented by highways, and 
so if one wants to know where pedestrians may cross a railway they can 
simply look at the tags on the intersecting way. So why do we have two 
separate tags for what is essentially the same thing (there are road 
crossings without gates and foot crossings with gates)?