It's that there's a lot of variation in dishwasher quality.

I used to live in an apartment with a landlord-installed $200 cheapie dishwashers that never worked.

Then I moved to an apartment without a dishwasher, so I bought a $500 one that I could plug into the sink. Worked much better.

After that apartment, I moved into one that had the same dishwasher that I bought, but installed. Worked great! Then I moved into another apartment with a cheapie dishwasher that was so loud I'd only run it when I left.

Anyway, the lesson is that you need to be a savvy consumer... And skip the cheapest models!