Why do "const inout" and "const inout shared" exist?

[Andrei Alexandrescu via Digitalmars-d]

Walter looked at http://erdani.com/conversions.svg and said actually 
"const inout" and "const inout shared" should not exist as distinct 
qualifier groups, leading to the simplified qualifier hierarcy in 
http://erdani.com/conversions-simplified.svg.

Are we missing something? Is there a need for combining const and inout?

Thanks,

Andrei