It's absolute bollocks all this protesting that your estate can be left to and divided how you please. That people should just suck it up, have no right to be hurt and that the assertion of it not being about the money is invalid.
Unless there are specific and moral reasons to not divide your estate equally amongst your children (and in a normal, loving family that will have been discussed and agreed amicably) then it is absolutely wrong to favour one sibling financially or disinherit.
This is often done to hurt and manipulate even from the grave. A way to get back at people, a way for others to benefit financially. To say 'well it's my right' is a bollocks defence.
Yes your money and estate are yours to bequeth how you please. But why upon why would you hurt and divide your children without good reason? It is about money to some degree but not wholly.
Siblings when they are innocent children seek to be treated equally. If my ds gets a treat, dd wants one too. If ds gets told off he expects dd to get a row too when she is naughty. It starts from birth, a desire to be loved equally.
Adults who haven't shared equality (and this does happen) as children still feel that hurt into adulthood. The money in a will isn't wholly literal but symbolic of past hurts.
Anyone who can't see that, or thinks it's okay to tear apart families without good cause is blind and ignorant.