Inheritance tax is only really draconian on semi-rich people, and rich people who die *unexpectedly*, or people who can't give up control.
If you don't die unexpectedly it is very easy to avoid IHT by giving most of your stuff away - that's the 7 year rule, but you have to give up control or else the assets may still be regarded as yours.
Any couple who expects to die with over £2M - well, their heirs - would benefit from estate planning which can significantly reduce the IHT that could be due, and anyway such people probably have an option to leave the UK, so by staying in the UK they are making a conscious decision to have IHT apply to their estates.
Also there is no IHT on gifts out of excess income, on certain business property, on certain unlisted shares etc., it's pretty easy to avoid if you really want to.