When I buy something, I don't complain it should be VAT-free because the income used to buy it was already taxed though. That's an everyday example of 'double taxation' right there. Ultimately, sums of money aren't discrete 'lumps' that pass through a tax barrier once and become immune to any further taxation. Another transaction happens, and the government get another opportunity to syphon it down. In this case, the money is now income for the inheritor, who has never paid tax on it, so it becomes subject to it.
I've never seen a good defence of inheriting huge sums of cash, it always boils down to "helping your kids/dependents out with a financial leg up", which is something that's likely already happened in their early life anyway if you've got that level of assets, plus it just helps run cover for the super-wealthy entrenching their wealth and privilege down the generations. A truly equitable society doesn't give talentless, brain-dead no-marks like Jacob Rees-Mogg positions of influence, but in the real world he's allowed free run at political & financial gain just because of his background and upbringing.
I don't want to get too forthright on this, I know most people won't agree as polling for reducing inheritance tax is always popular, even amongst people who would get no benefit from it. But if I could have made one change to human society in the early days it would be to remove the idea of leaving cash, titles, land etc to descendents - because the inequality and entitlement it engenders has been a massive contributor towards a huge amount of human suffering down the centuries.
