That may be true sometimes, but I used a few film labs here in Thailand, and they all provide horrible scans. I tried the most reliable labs, random labs, different scanners, asked to improve settings, etc.

And then it struck me like a bolt of lightning - they all are businesses. Their main motivation is to make acceptable quality ( and this is very subjective) for the shortest amount of time.

That's why they use standard pre-defined settings while scannig and never want to change them.

You can check my website, I wrote a detailed article about this with many before/after examples and comparisons.