It isn’t even that good at anonymity for the most frequent use case compared to alternatives. By far the most transactions that may benefit anonymity are local and involve relatively low values. Cash is a perfect fit for that and gives you even more (and a lot easier) anonymity then cryptocoins.

Cryptocoins only prove them selfs superior if the transaction is located to far away to conveniently travel, or involves such large sums that gathering or carrying as cash becomes inconvenient (or impossible). I would think that over 99.99% of people never engage in such transactions where they additionally require—or even prefer—anonymity.