Whilst it's an interesting thread to share experiences, in all fairness, with an overheard comment, we never know the context.
I don't 'bargain' or 'bribe' as a normal experience BUT I may offer an incentive if I want to change a plan to suit me: I want to get home very soon (whatever reason) so don't have time for the planned 'treat out' - but tell you what - we'll get a treat to take home instead. And then I would tell parents how helpful the child had been.
I am also careful around children under stress of some kind, when a change in usual routine or plans may be difficult. My parents came to look after my kids when I was in hospital and my 4 year old became inconsolable over the shape of the carrots that grampy had prepared that looked different to our usual ones. Grampy sensibly didn't insist on them being eaten and asked for 'help' the next day in getting them just right!
It would be quite different on a normal day.