When you attended your college, you were privileged enough to benefit from all those that attended your college before you. These alumni have donated money and built buildings to provide a benefit for you when you were a student there. You able to take advantage of these gifts when you were a student and you should feel obligated to pay that advantage forward to the next generation of college students.
I believe in humans' liberty. We can't make people do things in which they do not believe or interest! Even if that is sth good by itself, like giving to one's Alma mater. Universities/Colleges/Schools are either private or public. Private ones have received fees and attending those which are public/governmental are every citizen's right. Making donations is great, but forcing people is wrong!
No, they do not have a obligation to donate to their alma mater. It is their choice if they chose to do so.They have the right to if they want to or not. It is their own personal choice if they choose to or not to. A person has a right to chose who they want to donate their money to, if they want to at all.
I believe that people who earn and have ample amounts of money should donate and do good in the world to help humanity. However, I do not believe they should feel obligated to help certain institutions. While colleges are a great place to help out, it shouldn't be a requirement.
While a former student from a university may feel indebted to his or her alma mater for setting them on their way to success, they don't always have to pay them back financially, given that many may have already paid tuition to have the opportunity to study at that university. It can also be done by giving them publicity or directing other potential success stories to study there.