Why don't planes fly directly to their destination? Here is the flight path for B62554 from PBI (Palm beach) to JFK. This flight almost goes back on itself when off the coast of South Carolina.
I was wondering why this flight takes such a contorted path? Another example is B6242 from Havana to JFK, which similarly diverts out to see when near New Jersey then comes back at an almost 90 degree angle.
There are many reasons why planes don't fly direct to their destination.


Mountains (for smaller piston aircraft)
Traffic capacity and traffic flow considerations for the ATC center
Weather along the route
Preferred airway routings


For an analogy, cars don't drive direct to their destination for the same reasons.  Roads, I would venture to guess, would be preferred routings to your destinaiton.

There would be a traffic jam if everyone wanted to get to the closest airport for the Olympics at the exact same time.  Traffic flow considerations would dictate planes slow down or fly a different routing or wait till there is a time slot for them to land at their destination.