Barkley was invited by Bob Knight to try out for United States men's basketball team for the 1984 Summer Olympics. He made it all the way to final cuts, but wasn't selected for the team, despite outplaying almost all of the front-court players there. According to Knight, Barkley was cut because of poor defense.  Barkley competed in the 1992 and 1996 Olympic Games and won two gold medals as a member of the United States men's basketball team. International rules which had previously prevented NBA players from playing in the Olympics were changed in 1992, allowing Barkley and fellow NBA players to compete in the Olympics for the first time. The result was the "Dream Team", which went 6-0 in the Olympic qualifying tournament and 8-0 against Olympic opponents. The team averaged an Olympic record 117.3 points a game and won games by an average of 43.8 points. Barkley led the team with 18.0 points on 71.1% field goal shooting and set a then-Olympic single game scoring record with 30 points in a 127-83 victory over Brazil. He also set a U.S. Men's Olympic record for highest three-point field goal percentage with 87.5% and added 4.1 rebounds and 2.6 steals per game. Barkley was also part of an ugly moment in the 1992 Olympics when he intentionally elbowed Angola player Herlander Coimbra in the chest during a 116-48 rout of that team.  At the 1996 Atlanta Summer Olympic Games, Barkley led the team in scoring, rebounds, and field goal percentage. He averaged 12.4 points on 81.6% field goal shooting, setting a U.S. Men's Olympic record. In addition, he also contributed 6.6 rebounds per game. Under Barkley's leadership, the team once again compiled a perfect 8-0 record and captured gold medal honors.

Answer this question "Why wasn't he selected?" by extracting the answer from the text above.
According to Knight, Barkley was cut because of poor defense.