The high threshold is to avoid capturing family businesses. Personally, aside from the ease of avoidance, I think death tax is a pretty horrible concept. If you've paid tax all your life, have had no recourse to state pensions etc and your assets will continue to pay taxes after you pass, the government has little right to swoop in and take a % of your assets just because you carked it.
Look at Bill Gates, Buffett, Zuckerberg etc. They're donating their assets to a charitable trust (tax free) when they die to get around death taxes. Once the assets are inside the charity the earnings will be tax free. The government shoots itself in the foot.
It's no different to any any type of tax. I went to work all week, got paid and the government takes a third of it. The more I earn, the more they'll take. The difference is that these taxes directly reduce my ability to pay for things that I'll use now.
Estate taxes don't harm the people that have passed away - they're dead. The only people impacted are those that have received a windfall.
We are going to need to get the revenue from somewhere and excluding estate taxes from the mix leaves a bigger load to be carried by the living, breathing individuals raising families, running businesses, being part of the community...
It doesn't make sense to me that our whole progressive tax system is geared at those who have the means to pay, paying more, and yet estates should be exempt.