It also attracts more teachers as coaching a soccer team is easier, than a rugby team. As the rugby coach has to coach both the forwards and backs. In many cases therefore a rugby team requires two coaches to be a well-drilled outfit. In many schools, the less motivated teachers as like students, are presence in the soccer program.
Also, teachers are supposedly recruited for their teaching expertise, hence schools now indirectly recruit less sports inclined individuals.This issue is but one reason, why Rugby numbers are down and soccer numbers up. In the past schools would directly advertise, that the ability to coach rugby would be a distinct advantage in applying for a position. This rarely happens now.
It is one thing to have a liberal choice in a school sports program, another to have unmotivated teachers and students.