When you did a taste testing, they probably didn’t overcook the chicken and it tasted great. But when they cook for 200 people, the meat tends to be overdone.
This is why BBQ sauce is so helpful, it covers the dryness of any overcooked meat. Did you ever get a plated meal at a wedding and wish they added more sauce to the plate?
With plated meals, they need to be kept warm while the staff runs back and forth. Plus, maybe the meat sat on a plate while the potatoes were finishing up. All this leads to dry meat. BBQ on the other hand gets cooked in big batches and just marinates in juice.
Yes, some plated meals can be great, but also consider BBQ is usually cheaper and all the sauce options are fun. And with BBQ, guests can enjoy seconds!