My answer may surprise you, but if Jesus won't make any difference in the way you live, then you're right: there wouldn't be any reason for you to believe in Him. The Bible puts it this way: "As the body without the spirit is dead, so faith without deeds is dead" (James 2:26).
But when we truly believe in Jesus and sincerely commit our lives to Him -- then our lives will be changed! It saddens me that all the so-called "Christians" you've met only have a shallow or casual faith -- which isn't faith at all, as the Bible defines it. When we put our faith and trust in Christ, we see Him as He really is: the divine Son of God who came down from heaven to save us from sin's penalty and power. We also are committing our lives to Him, trusting Him for our eternal salvation and following Him as the master of our lives.
Christians aren't perfect; we still sin and we still fail in many ways. But we aren't content to stay that way, and we'll constantly seek God's forgiveness and help to live the way we should. My prayer is that you'll meet some people whose lives truly have been touched by Christ -- for they are all around you.
Most of all, however, I pray you'll focus on Jesus Christ, and not on other Christians. He alone is perfect, and He alone can give you hope and help for the future. Invite Him into your life today.