Many still get commissions or use larger conglomerates who pass on a healthy commission for international airfare. Sometimes they get special fares with the same or better conditions than the public gets for a lower price. It just depends. Not all international air fares are commissionable, but many (very many) are.
and upgrades, for example, first class for the price of full business.
priority waitlist clearance
etc
Unless markets are negotiated, my experience is not better fares through the agency, but consolidators can be used for better international fares.