Whilst I completely agree that as
Slippy78 and others say nobody should expect an inheritance and elderly parents (or anyone else) should spend freely to make their own lives and old age especially comfortable and enjoyable, or indeed donate/ leave a legacy freely to well established, transparently accountable reputable charities ... I think anyone leaving any kind of will, estate or legacy should be aware that if they don't treat their children the same (or all their grandchildren the same as one another, or even treat nephews and nieces the same as other nephews and nieces or whatever, though less significant than own direct descendants) there is an incredibly high chance of destroying relationships between the people they leave behind.
If you leave your house to your son and nothing to your daughter, or leave one set of grandchildren 10k each and the other set a piece of jewelry without value each then no matter how ungrabby those people are they'll feel that you didn't love them equally.
Inheritance destroys relationships between family left behind where it's ostensibly very unfair, because it usually looks like a continuation of life long favouritism and rejection.
Sometimes manipulation and coercion is done by aslow drip over a year or a decade and could never really be proved.
Unless you're a dependant or have evidence of illegality there's probably no point contesting a will in England or Wales no - but people leaving "unfair" wills should be reconciled to the fact that doing so might very well permanently destroy any relationship between the descendants they leave behind.