I'll spin it the other direction if I may......when Im dealing with a REPUTABLE company, I would rather have the shipping calculated like Mancinis and NationalMoparts do because their employees are using the actual dimensions and weight of my order to calculate the shipping charge, not just a computer algorithm.
Whenever I sell anything, I punch in the dimensions and weight, destination etc in the carriers website and give the buyer the price that the computer spits out, but when I take it to said carrier and actually ship it, 100% of the time the cost is never the same as what I quoted from online, and its usually higher.
Gimme the skill of an actual human over a program any day.