These requirements aren't in place for the purpose of making it hard to join the praise team. They are in place for the sole purpose of insuring any member of the praise team is there because God has called them to be there. It is believed that a person who is truly called to the ministry will do what's necessary to be properly prepared to minister.
While most of the members of a praise team are usually very good singers, it is a whole lot more than just a group of talented singers leading people in singing songs. It's easy for talented singers to perform songs well and get their audience to respond to their performance. Whoever, an effective praise and worship ministry draws the audience's attention away from the PT itself and onto the presence of God. The purpose of the praise and worship ministry is to lead God's people into His presence.
To successfully fulfill this calling, it is important to have the correct people on the praise team. It's not enough to just have people with musical talent. The praise and worship ministry needs people who are blessed with musical talent and who are called by God to that ministry. The praise team fulfills the role of "worship leader" by being "lead worshippers." A praise team's primary responsibility is to worship God as they stand in front to lead the congregation. In a sense, they are "worship instructors" to the congregation as they model the act of worshipping God. The PTs' desire is to create an atmosphere where worship has the opportunity to happen. Ultimately it is up to the individual to worship God, but the PT is there to aid in helping each one to draw near and experience the presence of God for himself