[plt-scheme] The role of proper and improper lists?

Based on everyones replies my current take on improper lists is that
you could indeed construct them if you wanted, by using 'cons'. You
may do this because you wanted a fixed-size list (for some reason),
but barring that, there are not general benefits to doing so.
Perhaps you would use use them to represent trees (?), but beyond that
I am not familiar with other uses. Improper lists are an option
because we are provided with 'cons; there is nothing more to it than
that.

Thoughts?