If the boundaries are not there it's clear at low level you monitor the ctaf or multicom
And what are we supposed to monitor when we aren't low level (i.e. when operating above 3000FT up to FLs)?
The
FIA; that's where we get a SIS and/or TFC info, FIS & SAR etc. And for that, the frequencies need to be published, and the boundaries are of enormous assistance. That's why the industry demanded they be returned.
In any case, whatever changes are proposed will need to be subject to a HAZID & ultimately a safety case, and I'm not sure all proposed will pass.