As far as I can tell, the rule really only exist because of the previous state of delta where fights and MP lynching would take place, but stuff like that rarely happens anymore, and maybe it's because of the rule, or just because the people who were engaged in that kind of stuff got banned or left.
round start is usually the only point in a round where marines WILL be around all their friends and comrades, and sometimes depending on the nature of the relationship, things can end up being misinterpreted.
This is part of my opinion on the rule, personally don't like it, but post whhat you think