make install with upgrades of older dependencies

["Dirk H. Schulz" <dirk.schulz%kinzesberg.de@localhost>]

When I run a "make install" in pkgsrc/somewhere/something and there is 
dependencies where an older version has already been installed, make stops.

Now I can fix this with "make install DEPENDS_TARGET=update".

Why does it make sense to set the default for DEPENDS_TARGET to 
"reinstall" which leads to the above behaviour?

This is just for understanding pkgsrc better.

Dirk