Powerful institutions especially.
USC is the primary political powerbroker in Los Angeles (and by extension Southern California, and thus by extension all of California).
They're the largest land developer and one of the larger employers in Los Angeles (city and county), and both Democrat and Republican mayoral candidates make sure not to cross USC's path, and USC has been caught in LA corruption scandals multiple times due to this [0][1][2][3][4]
[0] - https://www.latimes.com/california/story/2022-09-11/usc-la-m...
[1] - https://www.latimes.com/california/story/2023-12-19/lapd-chi...
[2] - https://www.justice.gov/usao-cdca/pr/mark-ridley-thomas-foun...
[3] - https://www.latimes.com/local/california/la-me-usc-george-ty...
[4] - https://documents.latimes.com/los-angeles-memorial-coliseum/
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Anecdotally, I and my SO seriously considered doing part-time grad programs at USC (something EngMgmt or CS for me and Medical for my SO) because of the legacy+donor boost (specifically donating to the Athletic Fund, Association Chairman Fund, Widney Society, Parent Teacher Circle, and a couple other donor programs) which could help any kids we might have in the future.
It's not "that" expensive to donate to USC to get the donor boost assuming your kid isn't an idiot - it's just a couple million total over a consistent period (5-15 years depending on when your kid is starting).
Glad to see we probably don't need to worry about that anymore, as I expect penalties for offending private schools to become stringent over the next 30 years, as us Latinos and Asians are underrepresented in legacy admissions but are now the plurality in California but also a swing demographic.
We're much happier spending a similar amount in actual philanthropy instead.