Why should you have to pay taxes at all
I mean, I would prefer not to.
But here's the thing. Assuming that death & taxes are inviolable, we will have to pay some taxes in some form. Inheritance/estate/death taxes (whatever you want to call them) are the least distortionary tax, precisely because everyone is going to die and there's nothing you can do to avoid it. It also strikes me as the most fair tax because its incidence falls upon people who didn't really earn the money; i.e., the heirs. For that same reason it strikes me as a pro-meritocratic tax. As opposed to, say, the income tax, which punishes you for being a high earner, the estate tax just punishes you for being related to a high earner.
Obviously estate taxes aren't perfect, and I wouldn't suggest that the government be funded 100% by estate taxes. And Poodlebrain can probably talk more intelligently than I can. But I am quite convinced that the efficient amount of estate taxes is something other than zero (which is what it effectively is now).