It’s to make up for the fact that when a game of 5v5 is played in an area that small and teams figure out ways to grab 6ft9 and larger players, you can just constantly defend. Meaning the game itself is faulty design so they keep on making up rules like bandaids trying to keep it exciting.

This is my biggest complaint about nba basketball. You are either guarding someone or you’re not. There shouldn’t be any illegal defense called.

The short answer is that the zone used to be illegal, so when they would catch you playing anything like a zone you would get whistled

Because David Stern didn’t want the ball double-teamed out of Michael Jordan’s hands

The short answer is that the zone used to be illegal, so when they would catch you playing anything like a zone you would get whistled

The ELI5 version:

• There was no 3-point line at the time of implementation.

• As a result, games were often grind fests on account of both lack of spacing and camping defenders.

• The league wanted offensive players to showcase their skills, particularly as the ABA came through and began pumping out a more free-flowing product.

The slightly longer story:

The league implemented defensive restrictions in waves, beginning with a 1967 rule change that prohibited defenders from camping in the lane for longer than three seconds without clearly guarding an offensive player. This could be attributed to a number of factors, from opening up the game to combating the dominance of Wilt Chamberlain.

The league then further clamped down on zone defenses toward the end of the 1970s, again in an attempt to open up the game in an era where paints were packed in hopes of forcing games to become mid-range snoozefests.

While the 3-point line made its debut in 1979, it’s power would not be realized for years after the fact, likely leading many to believe in the continued necessity of the illegal defense rule to maintain a balanced game that provided opportunity for offensive players to work their way to the rim.

In concept and purpose, it’s not altogether different from some rule alterations we’ve seen in the modern game, legalizing the gather step, loosening dribbling restrictions, and empowering offensive players to reap the benefits of initiating contact in certain instances. It was primarily in the name of providing an attractive product.

The main reason was to differentiate the game from college basketball and increase offense for a more wide open game.

People don’t realize, the game and shooting or where you shoot from is heavily influenced by the rules… always has been. Imagine if they made an illegal offense rule that said you were not allowed to have the ball above the 3 pt line for more than 3 seconds? There would be a lot less 3pt shots. Or what if they increased the size of the key by 25%? With no illegal D, and zones, they might push shooters out even farther. There’s talk about a 4pt line… go ahead and put one in, it won’t be used by anyone except a handful of people… it’ll be considered a “bad shot”… and coaches will discourage players from taking it… defenses will dare players to take it. Sound familiar? That’s the 3pt shot of the 80s and 90s. The game goes as the rules go. The league wanted to see more shooting, so they changed the rules… and the players adapt. It’s not better or worse, you just adapt to the game in front of you.