* Wiki doesn't want to look like they would be endorsing cryptocurrencies, which actually I cannot argue
It's not really good reason since they don't endorse specific country when they accept certain fiat. And it's rather ironic when Wikipedia promote similar ideology (free and open knowledge).
However, seeing Wiki as a pretty "hungry" organization - they do put big banners begging for money now and then - I think that's a losing move on their side. Although they've received "only" 130k worth of crypto as donations, it's much better than nothing.
It's possible they assume they could lose more donation from donator who strongly oppose cryptocurrency.