Actually, the ownership of gates by airlines (even under leasing arrangements) has some anti-competitive effects. Although this is the model used in the US and Australia (of the countries that I frequently visit), it's not universally used and most airports I see don't have this arrangement. It's very common to have gates allocated dynamically by the airport company rather than under airline control. In countries where there are ownership/leasing arrangements, gate ownership becomes an additional problem whenever competition issues arise (eg on takeovers or mergers).