There are many other reasons why using relations is superior when mapping neighbourhoods.

The simplistic way of using landuse=residential as a polygon to map a neighbourhood has got many disadvantages:

1) producing overlapping landuse errors on JOSM checking especially if it overlaps with an apartment lot also tagged with landuse=residential

2) overmapping actual residential land area because much of the land in the neighbourhood is used for purposes other than residential (eg retail, amenities, recreational, forest, lakes, roads, govt offices, etc)

3) GPS routers will route to the physical centre of the neighbourhood rather than the "social centre" of the neighbourhood.

Using place=neighbourhood as a relation and adding a node label into that relation to map a neighbourhood solves the above 3 problems.