Well from what I've heard as Ripple partners with more and more financial institutions and businesses they encourage them to run validators of their own. So Ripple expands its operations, the company running validators becomes less and less of a concern. Regarding the recommended UNL users don't have to use that as their UNL and according to Ripple's website: "Eventually, Ripple intends to remove itself from this process entirely by having network participants select their own lists based on publicly available data about validator quality."
And regarding incentives, there's no real incentive either to run Bitcoin full nodes but plenty of people still do because they want to help the network (often because they hold bitcoins i.e. have a stake). In the same regard, the companies and individuals who participate in the XRP Ledger also have "skin in the game" so to speak so are incentivised to make sure that the network remains healthy by running validators.

Also I don't think the requirements seem all that high. In order to be included in the recommended UNL you just need to be seen as a reliable validator: https://developers.ripple.com/run-rippled-as-a-validator.html#understand-the-traits-of-a-good-validator
And according to them the financial costs are "comparable in cost to running an email server in terms of electricity." The system requirements aren't too outrageous either: https://developers.ripple.com/system-requirements.html

Thanks for your perspective. Cheers.