In my experience, a very large percentage of people who write wills go ahead and split their estate between all the children as opposed to recognizing those who were really there for them through thick and thin. It doesn't make smart financial sense at all for a testator to leave money to the grandchildren unless it is in trust, as there is a huge penalty tax on "generation skipping" transfers.
I think testators wish to maintain family harmony after their death.
Of course, I'm all for spending every last dime. You can't take it with you and inheritance really brings out the worst in many people. Estates become even uglier than divorce in many cases!!
I'm seeing it now, and there isn't even a dead person, yet!
I figure if you want someone you love to benefit from your "extra" wealth, just give them "gifts" while you're still alive. That way there's nothing left for the ghouls to fight over when you're gone.