Someone please tell me why I shouldn't do this, or give me more reasons to do it

I won't go into the reasons I don't visit with my grandmother and step-grandfather, who are both still alive. They also broke promises to me, usually with the excuse of teaching me self-sufficiency. So I took that lesson. I'm so self-sufficient that I don't need them for money and I certainly don't need them for the other more important reasons that I don't see them. I am what they wanted me to be, independent. As for staying away because of the bad memories, that's fine, too. It's called toxic parents. I may be the only one, but I don't have a problem staying away from toxic family and don't feel a need to continue a relationship with them if it's going to cause misery, bloodline or not. Wounds heal into scars and they don't get better by picking at them.

Ron, I think you summed up how I feel much better than I ever could have, thanks. 

I hope everyones personal stories have helped you see that you are not the only one with family problems, not that you said that, but sometimes it just helps to see that others have been through the same thing or similar.  If you do not want to have a relationship with him, then good, dont... you all kind of seem toxic to each other.  He KNOWS no one likes him, and he deals with it how he will, just as you deal with your anger how you will.  All of that is just the way life is... hes not gonna change unless yall do and yall wont change your opinion of him unless he does, so I dont see this going anywhere.  I hope you take away the general consensus from everyone that while you may have many many reasons for not liking him... HIS money and what he does with it should not be on the list.  And sending a thank you card to him for remembering your birthdays is something you just have to do IMO.  That does not contitute a relationship whatsoever, just maturity and class.  I hope you reconsider and send him thank yous... again, he KNOWS, and I bet it hurts him... it really wouldnt hurt you to send him a thanks.. you dont have to call, just send a card.  I think as you get older or after hes gone and you look back you may regret not doing that.  You can still be tactful with him...
 
Sometimes with situations like this or people who are obnoxious or whatever I find it easier for me to handle properly by simply feeling sorry for them instead of hate.  I say wow I wonder what they must have been through to make them this way, what a sad thing.  I feel bad for them... it helps curb hate and makes it a bit easier to see the "light" of how to handle them IMO.

 
My grandfather wasnt a saint, and I wont go into that, but he died 2 yrs ago, and I am glad I was there. I have no regrets...
 
I dont think any family is perfect, and I know I have made huge mistakes in my life and am so thankful for forgiveness.
 
To forgive and move on in your own life wether or not you decide to be involved in his life will give you much peace.
Good luck.