They do, it’s called taxes.
If a government starts having a donation culture, it’ll just end up becoming a legal way to pay for government favours and exacerbate rise in corruption. (Corruption has been rising more and more now that local journalism is declining, which previously used to bust out local events, embezzling tax payer money by municipalities, etc).
Look at what has happened to colleges which have donations as a major chunk of their income, or colleges which subsidises local students education with international students.
Colleges have easier admissions for children of donators, local students are neglected for international student programmes (happening a ton in Canada right now, a lot of their previously reputed colleges are becoming blacklisted by employers as diploma mills, e.g Conestoga College, Ontario)
When you’re not the payer/customer, YOU. DONT. MATTER.
Corporate lobbying is making votes ineffective, politicians are listening to lobbyists and their donations to campaign funds, than the voter who gets out to cast their votes.
Donations are bad, and should be discouraged for powerful organisations like Gov, College, etc which have a lot of power.
You’re local orphanage would benefit from donations and there’s not much power in their hands over majority of society.
But when you introduce donation culture in more critical places, it becomes a method of corruption.