Miracles impress crowds, but there are very good reasons for miracles not to be performed.
Jesus healed people because He cared about their needs. It was an act of mercy when He healed a leper (Mark 1:40-45), but He wanted it to be kept quiet. When the leper made it known that Jesus had healed him, the association between Jesus and outcast lepers meant that Jesus could no longer preach within towns. From then on, Jesus had to remain outside settlements and the people went out to Him. This, however, was a complication to His mission.
At the beginning of Jesus’ mission, He spent 40 days in the desert without food. This made Him very hungry and the devil came to tempt Him at this point of physical weakness. Jesus could turn stones into bread, but He did not do it. He did not use His power to provide for His own needs.
We are told that the devil also took Jesus to the top of the temple and suggested that He throw Himself off since angels would catch Him (Matt 4 and Luke 4). The temple was a crowded place. If Jesus had jumped off the roof to be caught by angels, many people would have seen it and been in awe of Him; stunts like this in front of crowds of people would prove that He was the Messiah. He would gain popularity and star-status. Jesus did not do it, and He did not allow people to call Him Messiah.
Jesus could have opted for political power and gained all the kingdoms of the earth if He had set His mind to it. It would have been possible for Jesus to gain all this and then return to heaven miraculously without dying. He could simply have ascended, by-passing the cross. That would have been nice, and quite glorious. Instead He submitted to a non-miraculous, painful and inglorious death on the cross. Through humbling Himself He opened the way to heaven for us.
A demand for a miracle or for a sign is a Christian temptation. It can lay us open to the public display of miracle-working by charlatans. We witness people wheeled onto stages in wheelchairs who then leap up and walk off stage – but they are then found to have done it more than once. Fake healings and false signs destroy faith, and lead to cynicism.
It is a pitfall for Christians to ask for signs. The Lord only gives help in genuine cases of need. These become signs, but they were not asked for as signs. What is important is dependence on God Himself, and not on the reception of His gifts.