Why not? If I, as a parent, worked hard enough to make life easy for my child, who are you to tell me that I can't do it?(I mean in general, don't take this personally) I have paid tax on everything that I made, bought, or built - why would they pay tax on the same things again??
Following your argument, we should stop giving our children absolutely anything - you could argue that someone's child should not be given a phone or a car,because it's unfair towards someone else who had to work for it,right? But then why do you care - I worked hard to buy those things to give to my children. Anything else is irrelevant.
I can give you another example which makes me hate inheritance tax with passion - I know a family, which had a house which was owned by them for centuries. And then, when the parents died,they didn't have a lot of money, so the only thing left was that house. HMRC enters the scene -> children have to pay inheritance tax on the house. There is no money left,so they have to sell their family house, purely because people think it would be "unfair" for them to keep it. Absolute BS if you ask me.