GNU Awk - inplace editing

In GNU Awk I was looking for the in-place option (similar to sed -i).
I thought there once was some _simple_ option usable from the command
line. (Or am I misremembering?)

The manual now suggests to use a GNU Awk "inplace" _Extension_ for that
  gawk -i inplace ...
and
  gawk -i inplace -v inplace::suffix=.bak ...
respectively.

That's not exactly as simple to use as, say,
  gawk -i ...
and
  gawk -i.bak
so I suppose there's a reason for the added complexity in the handling.

Does anyone know that reason or remember a rationale? - I don't recall
any discussions about that...

Janis