The boundary rope in cricket is not the edge of the field. It is placed inside the perimeter, and where it sits is decided at the ground rather than by the laws.
The gap exists for player safety
A fielder chasing a ball at full speed needs run-off space. Placing the rope short of the fence gives a fielder room to decelerate without hitting a hard structure.
Minimum clearances are specified for this reason, and match officials check them during their ground inspection. It is one of the concrete items on that inspection.
At venues built for other sports, the clearance question is sharper. American stadiums have walls, dugouts and camera wells in places a purpose-built cricket ground would not.
Ground shape forces asymmetry
Few grounds are circular. The distance from the pitch to the perimeter varies around the field, and the rope has to follow a sensible curve rather than the fence line.
Where the ground is long, the rope may sit well inside the fence. Where it is short, it sits as close to the boundary as safety allows.
The result is that boundary distances differ around a single ground, which every batter and every captain accounts for when setting a field.
Broadcast and advertising claim space
Perimeter advertising boards, camera positions and cable runs all occupy the gap between rope and fence. That infrastructure is installed before the rope is placed.
Boards need a viewing angle to be worth their price, which means they cannot be pushed flat against the fence in every position.
The rope therefore ends up where the remaining space allows. Commercial installation is a genuine input into the geometry of the playing area.
Small changes have real effects
Bringing a rope in by a few yards changes which mishits clear it. Over a full match that is a material difference in scoring, and captains notice immediately.
Because the effect is real, competition regulations set minimum dimensions to stop grounds from shrinking a field to suit a home side.
Officials measure and record boundary distances as part of their venue reporting. The number is documented rather than left as a matter of impression.
What spectators behind it experience
Spectators in the front rows sit closer to play in cricket than in almost any other sport with a moving ball at speed. The rope is often within a few strides of them.
Grounds manage that with netting in the highest-risk arcs and with clear announcements about ball flight. The proximity is part of the appeal and part of the risk.
It also produces the sport's most direct crowd-player interaction. A boundary fielder standing on the rope spends an over within conversational distance of a full stand.

