Because they already donated to Wikimedia.

Two good times to recommend alternative charities: (i) on threads where people ask, "where should I donate my money", and (ii) on threads about disasters, when you have an opportunity to spur donations to targeted charities.

You almost certainly didn't mean anything by this comment, but you generally want to avoid the appearance of litigating someone's good deed as a missed opportunity to do a better deed. Donations to Wikimedia are a good thing, worthy of congratulations.