They tried anti-depressants after 2 years of his condition persisting. Trying a single anti-depression med is a perfectly reasonable attempt at treating the issue if the information the doctors have lines up with depression. Even when the medication does not work it usually provides them with more information so the solutions they try get closer to something which will work hopefully.

The entire field of medicine is heuristic, basically making educated guesses as to what the collections of symptoms indicate. You try something see if it works, if it doesn't try something else based on the information available. When your patient is a young child, you have different problems gathering that information than with an adult, kids may not notice or know how to describe something that is wrong, and adults will often omit things they consider embarrassing.

As someone who has had anxiety and depression for the 12 years since I graduated high school, the doctors I have met have been nothing like the notion of doctors you have, and while I am sure there are doctors whose first priority is pushing pills characterizing doctors in general as such I do not believe to be accurate. I've seen physicians and psychiatrists both of which tried to gather as much information as they could asking questions and running tests before recommending any treatment or even really suggesting what was wrong with me. They would often recommend things like more exercise, less time in front of computers and sitting, and finding hobbies after all tests came back showing nothing abnormal with my body. Both seemed to agree it was probably not a physical malady with physicians eventually recommending psychiatrists and psychiatrists recommending psychologists. Every time after a couple months of therapy not working they would try another; they were very hesitant to recommend medication. When they did they would have me check in weekly to give them updates, always switching me off of it if I indicated any side effects or just that things hadn't gotten better after a period of time in which it should. Eventually I would give up and stop trying new treatments even though they indicated they had not exhausted all options. After a few years I would try again.

Only recently, after starting up this chain of diagnoses again about 8 months ago, did I find relief. The psychiatrist tried yet another therapy and two medications, which I had not been on before but were similar to the ones which had more positive effects previously. Both wound up having the same negative side effects. He then reluctantly tried a third, which was in a completely different class of meds, saying he tries his best not to prescribe it due to it having nasty withdrawal. Low and behold, 2 weeks in for the first time in 12 years I was feeling like I remember normal being on month 4 now and still feel great.

Different things work for different people because depression and many other things in the medical world are effectively a name for a collection of symptoms and not a specific malady. The doctors I have seen seem to recognize that and respect that, and generally seem to prefer non-medication based treatments when they have hope it would work.