Taxing the rich 💵

I came across this meme today.. 
I couldn't help but ask "why?" 
Now let me start by saying I am politically, governmentally, and economically inept.  They are not my strong suit which is why I am asking you ladies... 
Why do we keep wanting to raise taxes on the rich? Just because they have money? It's their money and I feel like they should have a right to it, whether they want to be philanthropists or not. Why do we rely on them to help fund our country? 
I just feel like something must be flawed in our economic system if we have to rely on taxing the rich to help our society out 😕 
Yes I am posting anonymously, because I am afraid to get rude comments rather then help in understanding all this.