Because if they don’t worst things will happen. Humans are greedy and selfish. Blocking honest productive means to produce wealth will make them earn wealth through other means.
Just look at other countries where governments redistribute wealth. Look at China during Mao.
Why would some people work hard all their life if he cannot inherit his wealth to his children. If every kids have the same chance to succed, why should I work harder if I am not going to either have more kids or my kids won’t have better chances?