Why do they play by fiba rules?
FIBA is a French acronym which stands for 'Federation Internationale de Basketball Amateur'. In English, this is 'International Basketball Federation'.
That means that international players follow those rules..
NBA is the National Basketball Association.. Only for people in our nation..
We have 13 players from our country playing in this and the rest of the people player are international.. They outweigh us...
They made the lane trapezoid to give the offensive rebounder a better chance (on free throws). The other countries were playing basketball before the three point line was made, since the nba did it they felt they should do something similar but they didn't do it exactly the same. Since no every country had the same rules or length of the three the French decided they would make a uniform set of rules that all team would follow when playing against each other. In other countries their is a bigger emphasis on being a team and a team should play defence together instead of being on an island at times like when playing man, so they let them play zone.
"All I'm saying is why does fiba need to change the rules in the first place? The rules were already invented."
http://www.nba.com/analysis/rules_history.html
For the same reason the NBA has changed the rules of basketball over the years. The game has needed to evolve. Leagues needs to evolve as do rules and how rules are interpreted, and the particular rule changes are often put forth to fit a certain situation.
The reason you have mostly been given insulting responses is that the premise of your question is idiotic and xenophobic. The game was founded in the US, but the NBA does not have autonomy over the sport worldwide. Heck, the NBA doesn't even have control over the rules of high schools or the NCAA. I think the NBDL even have experimented with some different rules from the NBA.
The game was invented in North America, this is our game. Why would it be played with different rules? They should play by nba rules, with nba refs in the world championships and olympics. It just doesn't make sense.