If everybody must be equally well-off all the time, there can be no significant movement up or down.

Reeves has declared war on inequality – but it is the engine that drives success by Janet Daley.  

Written in the context of the evils the British Labor government but pertinent generally.  Emphasis added.  

The great social evil now is relative poverty. Having succeeded in eliminating the mass hunger and life-threatening conditions in which so many once struggled to survive, we must finish the job and go on to abolish inequality which is the great injustice of our own age. The inference is that some people being relatively less well off than others is the precise moral equivalent of people starving to death while others feast.

Ironically, it is the great success of free market economics and the unprecedented mass prosperity it has produced which brings this reckoning. The economic system that has delivered more people from poverty than any previous one in human history is now attacked for failing to bring everyone’s lifestyle to the same standard all at once. There are some real problems with this. If everybody must be equally well-off all the time, there can be no significant movement up or down. That would rule out what might be seen as a natural trajectory from less successful to more successful, or from early struggle to affluent independence, perhaps involving personal resourcefulness or a climb up a professional ladder.

Relative poverty, so long as it is not permanent, is the obverse – the other side of the same coin – of social mobility. If there is a political guarantee of economic equality, as there was supposed to be in the old Soviet societies, the possibility of individual self-improvement is lost. For some people to be better off than others is not, in itself, morally unacceptable: their affluence may be a reward for talent, effort and risk-taking. (The argument that such traits are themselves unfair advantages is beyond ridiculous: it is positively pernicious.) Of course, they might have achieved their success through unscrupulous means, but that is the kind of moral affront which laws and social disapproval are intended to prevent.

The idea that anyone who is significantly better off must be, by definition, immoral is what lies behind the logic of a wealth tax – which is, in effect, a success tax. This is the real crux of the matter. Personal achievement and self-improvement are among the greatest satisfactions life has to offer. The possibility of moral agency and the scope for taking individual responsibility are probably the defining attributes of emotional maturity. We have spent a generation or so arguing about whether the government should guarantee equality of opportunity – which would provide as many people as possible with the chance to experience these things – or equality of outcome which would, by definition, eliminate them.

Relative poverty – which is to say, being less well off than some other people – is not, in itself, a bad thing, so long as it is temporary and remediable. It should be something that you can escape, leave behind, look back on as a formative time. (You may have guessed that I speak from experience here.) But the possibility of it must exist.

The emphasized text gets to the point I harp on - All systems need variance in order to evolve.  You can only have zero variance in contexts of zero change.  If the environment or context is itself subject to change, then your system within that environment needs variance to allow the evolution of the system to adapt to the changes in the environment.  Darwin's theory of evolution has application beyond the biological world.

Any ideology which insists on removing variance between individuals in order to achieve "equality" are guaranteed to fail.  Social systems are subject to exogenous change and therefore there needs to be variance (inequality) within the system to allow it to evolve in the context of those exogenous changes.  By disposing of differences, you guarantee the eventual collapse of the system.