Here are a few reasons I disagree with you. Let me know what you think.

1) The point of gathering wealth is to somehow make yourself happier. Without this, wealth is meaningless. One of the things that make many parents happy is the knowledge that their kids will be well off. If you take that away, you are removing one method of achieving happiness through wealth.

Now, as a society, we do eliminate methods of gaining happiness through wealth. E.g. we don't allow you (legally anyway) to use your money to hire an assassin. There are other, less glamorous limits as well, such as limits on what you can buy in the stock market, etc... Each of these limits has a reason (or should anyway, if it doesn't, we should get rid of the limit) that relates to harming society. You seem to be saying that the money could be better used in other ways by the government. Although I question if the current incarnation of government would do so (in any country) I'll grant the premise for now, but still disagree.

I disagree because not only is making one's kids well off one way to gain happiness through wealth, it is a hugely significant way for many parents. If you want to change the inheritance laws, society needs to weaken the connection between parents and children, something which I don't believe would be a good thing.

2) You seem to think of inheritance as money. Its not just money. Inheritance is also property and rights (and other things? I'm not sure). With your system, after a few generations the government would own everything. Sure, we could find a way to have the government disperse these properties and rights, but this would be a very cumbersome system that would need to be frequently implemented and its unlikely to produce fair results. For example, lets say we do an auction when each person dies. How would people place bids? How can we make sure everyone is allowed to place bids? How can we make sure the rich don't use this to pick up things at way under market/reasonable value because they happen to be awake during the bidding process? Etc... You can probably create a system that solves the questions I asked, but it would be cumbersome and difficult to manage.

The problem is even worse with rights. Lets say I own some long term debt... i.e. I have the legal right to receive cash from a someone periodically over the next 20 (say) years. Now, if I die... who gets the rights to that cash? You want to auction that off as well? Who even knows I have that right? I may have it written down, but it may just be an informal contract with someone. This can be a problem even now, but with wills, people will want to write it down for the sake of their children.

3) In reality, I don't accept your premise that a governing body would do a better job with the inheritance. We see now that so many government programs are a waste (even though many are a success. I'm not being anti-government here). Do we really want to trust some body to use this money? This leaves so much room for error. Also, there are individual/family needs that won't be taken into account. The sick significant other is a big one (mentioned by @russell) and I'm sure there are more.

4) Think of how weird the situation is. Say you save up for your kid to go to private school or college. If you stay alive during that period your kid gets through it without debt. But, if someone hits you with a car, suddenly your kid will need to get loans? That doesn't make any sense. To reconcile this, either you need to do what you said and limit what kids can get while the parents are alive, or allow inheritance.

Lets say we go with option 1 (limiting what kids can get while alive) and say the private school is a religious school. Now, the parents are sending their kids there because they want to instill certain values. So now, we are limiting the parents rights to instill these values? This is not something that should happen in a free society.

Just some thoughts...