Are you kidding? I get fed up with self-serve in many businesses- usually it comes with a crappy interface anyway.

I have seen little "pantries" in Business Class on BA- very nice to go back there and get water or snacks. Some practical reasons not to make it 100% self-serve:

1. Way too many people walking in the aisles.
2. I'm sure they want to limit alcoholic beverage service to that served by FAs so it can be controlled. Many air rage incidents include too much alcohol.
3. Sanitary reasons- too many people poking at food (think of buffets) unless it's all pre-wrapped and that limits freshness and variety.
4. Portion control. You know there will be someone who will scarf up all the expensive stuff.