Only because the whole process is a lot of hassle and work for everyone involved, so it can be used with a primary purpose of chicanery rather than actually getting your legitimate claim.
If a lawsuit could be resolved quickly and fairly with little effort on both sides, I'm sure the limit for when it would be worth it would drop. I'd consider that a feature, not a bug.
And it is very easy to verify "1+1=2" or "amount + amount X 0.12 X number_of_months".
But my point is that meat contracts are very expensive to draft and enforce. It is not worth to sue someone in China over $50.