Some subset of casual fans continues to perceive the NBA as a one-on-one league. This notion could be a vestige of the iso-heavy 1990s, an extension of the grossly general characterization of NBA players as "selfish" or merely a byproduct of the pervasive focus on player-specific matchups.
But contemporary professional basketball is anything but a one-on-one endeavor. Ball handlers are forced to fight through an initial line of defense only to deal with a complex arrangement of help defenders, schemed to provide the most resistance possible.
The league's best offensive teams are those with systems geared not toward beating one defender, but five. Likewise, the stingiest defenses rarely leave a single stopper out on an island; there are contingencies on contingencies on contingencies, as to guide the instincts and talents of five players into a single, cohesive whole. An immense amount of instruction and preparation goes into defending at an NBA level, and it goes well beyond the simplistic notion of a player keeping his man in front of him.
For a glimpse into the complexities of that world, check out the above clip -- a segment of NBA TV's Real Training Camp, featuring the Brooklyn Nets. Lead assistant coach Lawrence Frank walks the Nets through some of the basics of their coverage: lock-and-trail principles, who is responsible for communication in specific situations, the triangular formation that defines Thibodeauian defenses. Systems are built on layers upon layers of such specificity, all of which is lost on those who see the game as a series of one-on-one confrontations.