Repat,
There's an old expression "cut off with a shilling".
If you did not mention in your will a person at all then it might be contested that said person had been accidently missed out. By mentioning them and giving them a shilling it made it quite sure what yuour intention was.
Quite often such persons had already been given large sums of money, or the family business, or farm, or property, so they may not have been disliked or disadvantaged.
Bryan