Well, everybody is correct: antibiotics should only be used for bacterial infections (not viral or fungal) and a culture should be made to make sure the antibiotic prescribed is the right one BUT when dealing with birds, we are dealing with very fast metabolisms and bacterial infections can run rampant and out of control in a matter of days, that's the reason why avian vets give Baytril on the first visit. It is a very wide spectrum antibiotic that serves very well in lots of different bacterial infections and, in truth, most people would not want to pay/wait for the culture.

If the birds are kept in a clean environment, with fresh, organic food and a good varied diet, with plenty of exercise (so the lungs don't atrophy) and all birds are quarantined and tested before integrating them into the community, there will be very few times when antibiotics are needed. So, it is all up to us (as everything else with captive birds).