I was on a recent Delta flight and they had cleaners come in and wipe everything. Not sure if it's something everything flight. It was to Atlanta where it's their hub so maybe they have a dedicated staff there.

I didn't see the video of clouds from the seat but IMHO that's prob common...I remember as a kid hitting office chairs and seeing dusts puff up.

The article cited Ryan air a lot, but like Frontier Airlines, I imagine cheap tickets means bad customer service as their staff is paid just enough to do their jobs but not care...that's talking from personal experience of how rude and unknowledgable Frontier staff (not just one but all interactions on my one flight) was compared to other airlines.