> I could much easier get permission to buy a $5k piece of software than donate $5 to an OSS project that powers out largest project and has been maintained for 10 years by a single person.
Because business has it's own logic. If you invest $5k in a product, you are expecting the return to be customer support, quality control, timely bug fixing, "enterprise" features, feature request priority, legal indemnification / due diligence, etc. You make a business case to justify the expense, with the expectation that this is going to provide a return (eventually) in the form of revenue, time/cost savings, etc.
Donations in and of themselves don't provide any obvious return. If the project kept a "business case" page that includes what the donation goes to and shows the direct benefits that come from donation, it's much easier to justify the cost. And you might think "can't they just write off the donation?", but the project would need 501(c)(3) status, and it's apparently quite[1] hard[2] to get OSS approved as such.
[1] https://web.archive.org/web/20221201141451/https://opensourc... [2] https://www.mill.law/blog/more-501c3-rejections-open-source-...