Multi-boxing rule question

[Frug]

I have no intention of breaking, bending, nor trying to get around the "no boxing" rule, nor do I want to whine about it; your server, your rules which is fine.

My question is simply, why does this rule exist? Was it ever allowed and abused, or to enforce grouping, or something else?

Again - I'm 100% fine with the rule as it stands, and am merely curious from a historical perspective.

Thanks!