Why didn't the ninety-nine sheep realize they were lost?
Because they were self-righteous and self-content, they assumed they were spiritually alright. Though they were without a shepherd and desperately lost, they went on their way, never recognizing their true condition. Their confidence in their own righteousness blinded them to their need for the true shepherd.
Les explains that the ninety and nine represent the Pharisees, the Sadducees, and the majority of Jews. They were without a shepherd, but they did not know it. They were so self-righteous and self-content, like a bunch of sheep in the wilderness going from clump to clump, thinking they were alright, but they were desperately lost. The vast majority of Pharisees and religious Jews went on their merry way, not knowing that they were lost. Only the small remnant of Jews who followed the Lord and became believers realized they needed the true shepherd.