Why Not A Wealth Tax?

The idea of a Wealth Tax had been mentioned a few times but nobody has ever implemented it but Keir Starmer and Rachel Reeves are widely thought to be considering it and most tellingly have refused to rule it out to help balance the books when asked about it.  
Keir Starmer has repeatedly said that those with the broadest shoulders should carry the largest burden which tugs at every old Socialists heart as what we should be doing anyway but how would it work?
A wealth tax, so it was explained, is aimed at reducing economic inequality to redistribute wealth and to raise revenue and is a direct levy on an individual's, household's or business's total net wealth, rather than their income.
Advocates of the tax propose an annual 2% tax on wealth above £10m which has been calculated as affecting 20,000 people but would raise £24bn a year which is equivalent to putting 2p on income tax.
In Europe France, Italy , Norway,  Spain and Switzerland have a Wealth Tax but the argument is that if you squeeze the rich, then they bugger off elsewhere with their money but also up for consideration is a one off Wealth Tax and the one shot economic boost that would give but another alternative is to just get the tax rates fair in the first place.
At the moment the British tax system seems tilted towards the rich with only the higher rate payers receiving tax relief for Gift Aid and pension contributions, the basic rate tax payers get nothing for charity donations or putting into a pension and anyone earning up to £125,140 pays tax at 40% while anyone above that to any amount only pays an extra 5%.
Whether it is a one off or a repeated annual tax then i can't see why Labour are just thinking about it when the options are annoy 20,000 people and raise £24 billion or put 2p on income tax and annoy every working person in the country.