Why is an explicit footnote mark not printed in the footnote?

[Urs Liska]

As per NR 3.2.4 it is possible to specify an explicit footnote mark as 
opposed to the automatic number. However, in this case the mark is *not* 
repeated in the footnote itself. The examples in the section show that 
this is not a bug but known behaviour:

\footnote "*" #'(0.5 . -2) \markup { \italic "* The first note" } a'4

But I'd like to ask if there's a reasoning behind that. I can't think of 
a case where you'd not want to have matching marks in the annotation and 
the footnote. Wouldn't it be better to have that automatically, like 
with automatic numbers?

Urs