Get real will you, when kids are still at home at 18,19,20,21,22+ they are not kids any more they are adults and need to either leave the nest or contribute, not everyone is loaded and can finance 3+ people forever.
You do not need to be loaded at all. And kids will generally help out in retirement/old age.
At 18-mid 20s is when you are earning the least and have the biggest costs, as parents you should want to help kids out as much as possible. I'm very grateful for my parents to have this attitude and if I have kids will pass on the same attitude.
Charging really is poor show, old fashioned and un needed. It shows/teaches zero money control. Even 25% once a month is in no realms like reality if budgeting over a whole month. There's no struggle to pay it and no balancing things to pay bills even at end of month, it really is nonsense.