http://maldomapyy5d5wn7l36mkragw3nk2fgab6tycbjlpsruch7kdninhhid.onion
There are two main reasons for this. First, generating anonymous addresses for each found block is very CPU-intensive. Second, the mining reward is public knowledge for everyone and since we generate a new transparent address for every found block, there is no real need to use a shielded one.