Cows will wander from pasture to stream and back again as a group, but sheep all wander in their own direction and get lost. This is a serious problem because sheep are unable to protect themselves - they have no natural defenses. Cows will protect their young, but sheep are unable to do that either. Sheep cannot even give birth by themselves. If he waited until morning, both mother and baby might have died.
Sheep are dumb and helpless.
Without a shepherd to protect them and lead them, they will die. When Jesus got off the boat and was confronted by thousands of noisy people clamoring for His attention, He was not annoyed or angry - for He saw beneath the surface. He saw people who were ignorant, lost, and helpless. He saw people who would die without a shepherd to teach and guide them. Jesus knew that they came to Him because, like sheep, they knew who their master was - and Jesus could not let them down.