Think about it like this. Imagine when you were poor, or imagine if you were on the losing team at one point in your life.

How did it feel to hear from someone who was flashy, rubbing it in your face or being a show-off. Not good right? So ask yourself, why would you not want to be humble to others? By not being humble you make others envy you, make yourself a target, more hated, and less likely to give a positive impression to others. To each his/her own I guess!