There's multiple advantages for someone who is rich even with grants:
* Time to practice their craft for years+ without worry about daily necessities. This includes getting the best training and personal tutoring to reach their full potential (whatever it may be).
* Knowledge through connections of how to properly write a grant that is going to be accepted
* Possibly knowing the people making grant decisions personally (or through family). Nepotism exists everywhere.
* If grant comes from a non-goverment institution. Family ability to donate to institutions increases their chances of picking kids for jobs or grants. If you rely on donations would you pick a poor kid who will cost you money overall or a rich kid who will actually make you money in the long run?