Why ask for private donation address?

[nonsh]

I've seen people asking for private donation bitcoin addresses. Why not send it to one that is public? Does this improve anonymity for the sender?

Lets say the receiver provides a private donation address. When the receiver forwards it to it's public donation address, this is not of any help?

[Birdy]

It improves the senders anonymity, because everyone can see the public transaction and all connected addresses.
If the receiver sends it to the public address and it was the only other transaction, it didn't help much though ^^

[Elwar]

You may not want the government to see the donation address.