In the next version we'll clarify zcash shielded transactions are optional. Fwiw it's used by 28% of tx according to https://explorer.zcha.in/statistics/network and comments above, not "rarely used"
I'm not certain the source of these shielded transactions but the vast majority of value seems to be in unshielded transactions. Transparent value (unspent TX + unspent block rewards) = 1,070,918 while shielded value = 42,588 or around 4% of all value. That sounds like rarely used for transactions of any value to me.