I think that many children see rewards as sign of parental approval/ love even if the parents do love them unconditionally.
Certainly they can if bathed in fulsome praise/reward for each and every mediocre, minor achievement, yes. Because they know that the praise doesn't fit with the degree of effort or goal attained, and worry that their parent has a false image of their capabilities/who they are and if/when the truth is revealed they will be rendered "a disappointment" and somewhat unlovable.
But there are degrees of praise/reward. It doesn't have to be all or nothing. In fact all or nothing has the potential to cause more problems than it seeks to avoid because edging towards extremes leads to blind spots where dogma can take over and blind people to the obvious conflict between what they believe is true, and what is happening right in front of them. As you can see from what some posters are revealing in their posts about how their parents choices resonated with them. I don't doubt those posters' parents had the best of intensions, but it does look like they were less capable of knowing how it would affect their child than they believed themselves to be.
My son at the age of eleven is moviated enough to do best at his school work without having to bribed like one of parlov's dogs.
I think that is a confusion of two separate things.
To set a scale of known rewards like a trial of breadcrumbs in order to modify behaviour is one thing.
To surprise somebody with something in recognition of something that you know they pushed themselves hard to achieve, another.
The second isn't the best cunning plan in the universe in terms of bribery, because it is unknown to the rewardee until post accomplishment and thus paid no part in stimulating the behaviours required to achieve said accomplishment.
Renouncing bribery doesn't mean you have to renounce all and any rewards.
There comes a point moviation has to be instinctive and parents need to back off and offer a different type of support to presents.
The trick there I think is to realise there is no single point. There isn't a magic moment where you can count on letting go and staying let goed. There may be periods, (they may even be long) where a child's intrinsic motivation is high and does the job. But that can wax and wane as kids go through different ages and stages. Or it can appear and vanish based on external events, influences and pressures.
I don't think parents can always afford to be that fussy which tool in the parent tool box they will use in a crisis. And that includes surprise rewards, and yes, even bribery in the short term to get over a hump that could otherwise send the train off the tracks.
I'm hanging on to almost all and any potentially useful "being a parent" kit I have ever come across and keeping it in my toolbox, just in case one day I need it. I was a perfect middle school child....that turned into the teenager from hell, so just in case nemesis has me in its sights I want a well stuffed bag of tricks by my side.
I think there can be a problem with having overly fixed philosophies when it comes to being a parent. It can leave you up shit creek, looking at your carefully crafted oars, wishing you had held onto the formerly much despised bucket that was jettisoned years before, because you never thought you'd need it.