Ugh car tuning. I'm hoping someone on here can help my understanding because I feel like this situation makes me raise eyebrows similar to the audiophile commun

Ugh car tuning. I'm hoping someone on here can help my understanding because I feel like this situation makes me raise eyebrows similar to the audiophile community. In the Subaru tuning community, there's a company called Cobb that sells a product called AccessPort that you plug into your car and change its performance using a map file. Cobb themselves include off-the-shelf maps designed to fit vehicles with varying parts and varying conditions, and you can also pay a professional tuner to build a custom map for your car, which you would want to do if you have custom parts that an off-the-shelf map would not account for or if you have a very specific tuning goal. Here's the issue that I've been confused with: the community tends to advocate for using a pro-tuner over an off-the-shelf map whenever possible - even if your car has the same exact parts specified in the map notes, and even if your climate and elevation are the same as specified in the map notes - because "every car is different". If I don't have exotic performance goals + I have the parts supported by a given OTS map + I drive in the supported climate, why should I trust some rando in his garage to make a map for me, over Cobb who sees way more vehicles and configurations than any single shop ever could? A lot of the time reading these forum post endorsements sound like "the tune is so good this guy is totally a scientist yo". Anyway, partially a rant but since we're talking about enthusiast communities thought I'd share and I really am interested to learn!