Conor once bubbled...
( I could be wrong, but I only see a CESA as the first out-of-air option at shallow depths).
I guess the question is 'What are the reasons for ditching a weight belt ?' followed by ' What should a buddy do ?'
I disagree. I don't think that an Emergency Swimming Ascent is an option if there's a buddy in view/communication range. The risk there far outweighs a safe ascent....even if you do have to choke down a little water. That should really be an absolute last resort.
As for reasons to intentionally ditch your belt, I agree with genesis....I just don;t see any other reason other than an ESA.
Point is to make sound judgement and if poissible prevent there being any victim, but not endangering yourself in the process.