Inheritance Tax has to be paid before the estate is released to the beneficiaries. If it isn’t then interest is charged.
£100 may seem like a trifle to many people, but there are some who would struggle to find even that to pay an upfront tax. The longer they delay, the more interest is charged. So by being too poor to pay IHT upfront, the beneficiary would be charged even more and receive even less.
Some people really do live hand to mouth.
If the beneficiary received a car and some cash valued at £10,000 under your proposal they would need to stump up £1,000.
If they received a house valued at £200,000 they would have to pay £20,000 before they accessed the inheritance. You may have that sort of money sitting idle in your bank account, most people don’t.
And if the rumours are correct and Capital Gains tax is charged at income tax rates on homes with the inheritance exemption removed, then after having taken out a loan (if they are able) to cover the £20,000 IHT fee, they would also lose 20% (if a lower rate tax payer) to CGT charges on any increase in value between inheriting the house and being able to sell it to pay back the loan taken out to access the inheritance in the first place!