is that people who have their bitcoin without KYC, and we have a few on the forum, will probably prefer to donate dollars to deduct the contribution.
At least it is a reason to use Bitcoin as a currency and not as an asset or stock to get more profits.
The entity you are donating to will likely convert any coin you give them into USD. They will need to pay their bills and further their cause, which will ultimately be denominated in USD.
Personally, I see it as an encouragement for people to spend assets instead of converting them to dollars, and not all charities will convert Bitcoin into USD directly.