why oh why does calling Right, Left or Mid on a TDes give you a TPtrC?

Here's an example (which doesn't do anything useful) illustrating the reason for my discontent:

void method(TDes& aString)
{
   aString.TrimAll() ; // that's fine
   (aString.Left(3)).TrimAll ; // this should be fine but it's not because Right returns a TPtrC
}

If I wanted to accomplish the above I would have to go through the shenanigan of copying the right part of the data into a buffer and then creating a TPtr to the buffer and then calling TrimAll on the TPtr.  But then that doesn't modify aString directly (it only modifies the buffer) so if I wanted to modify aString directly, I would have to copy my buffer back into aString thus overwriting the original contents of aString.  Ugh.

Any comments?  Of course I might be just horribly confused but I think from a logical point of view, it's terribly inconsistent to have Right, Left and Mid return a TPtrC and not a TPtr when called on a TDes.

Thanks,

Nikolas.