As of the end of 2014, Texas has 825,957 license holders. With a population of 26.96 million, that's 3% of the population.
But, as you point out, the real issue is that most people don't bother to get a license. Since Texas is a Shall Issue state, the real issue is that most people have no interest in carrying, whether open or concealed.
I wonder what percentage of that “ don’t bother to get a license” group is comprised of people who don’t think the government has the “right” to tax and license citizens, based on the “shall not be infringed” in the 2nd amendment wording.....
or just plain out do not want their name on another government list in case of future “confiscation.”