A small proportion of that 9.2% could be members of the Amish community, who rarely have driving licences, and are probably reluctant to use a photographic form of identification anyway. According to the
Young Center for Anabaptist and Pietist Studies at Elizabethtown College, there were 61,270 Amish in Pennsylvania in 2011. Of course, that includes children too young to vote. Large families mean that under-18s often make up more than half the population of Amish communities, so for a conservative estimate I'll assume that only 20,000 of that population were over 18. That's less than 3% of 758,000, and even if the entire Amish population were adult, they would be less than 10% of it, so the vast majority must lack the cards for some other reason.
If this whole voter ID problem is a deliberate tactic by the Republicans, they may have damaged their cause somewhat, since the Amish, when they vote at all, usually vote Republican, due to the party's 'Christian values' and 'small government' reputation. In the
2004 Presidential election, the Republicans in Pennsylvania made a special effort to gain the Amish vote.