I guess you are talking about low diff coins (around diff1). These coins are profitable only theoretically. In praxis, we made several tests on them and noticed, that we lost many shares on these coins. Our coin_select has many conditions, that must be met and one of them is smart share distribution - thats why we skip these coins. We dont waste our miners shares - they are too valuable

By the way, we welcome any ideas about new coins, that can be added