How come some churches are okay if their members smoke and occasionally drink alcohol and others make that a restriction?
Each church has the duty to make a decision what will be required to become a member of that local church. Almost every club and organization does the same thing regarding membership such as the Lions Club, Kiwanis, Eagles etc. A church is supposed to be a group of people who have first of all have made a personal commitment to accepting Jesus Christ as Lord and Savior. To be officially a member of that church they may require not only that commitment but they may ask for some other commitments like you mentioned as a outward evidence of a person's convictions. Some things should be expected to be allowed and others things not allowed in order to claim full membership. Let me encourage you to always ask the Holy Spirit for wisdom and God's Word for guidance before you join any club or organization and I would apply that even to a church.
We have been encouraged many, many times in Scripture to pray, to call upon the Lord, to pray without ceasing. God wants us to always look to Him and to talk with Him concerning our every situation. There are also demoniac spirits who will try to steal, kill and destroy everything God has planned for you. When you asked this question I felt that the Lord urged me to say, "It could have been a lot worse if you hadn't prayed." Prayer is our direct connection to our heavenly Father. Don't let the enemy steal your connection with God. No matter what may come your way, continue to pray and see what God will do. Your prayers release the hand of God to move on your behalf.
How can I help my friend? He says that he loves God but he gets drunk on a fairly regular basis for over 20 years. He is very sorry and embarrassed afterwards and says he wants help.
Your friend saying he wants help is a very important first step. Recognizing our need for a savior, for someone to help us when we can't help ourselves is part of confession. Your friend is in bondage. He is captive to this addiction. Jesus said in Luke 4, "The Spirit of the Lord is upon Me...He has sent Me to...proclaim liberty to the captives...to set at liberty those who are oppressed." His addiction has set up a stronghold for many years that only the Holy Spirit can now break to bring freedom. Encourage your friend who says he wants help to truly be willing to seek and receive the help that is available. Teen Challenge is a program that I personally endorse for your friend. They deal with the root of the problem and not just the symptoms. Contact me if you want further information.