I can confirm from a pilot friend at another airline, that lazy FA's encourage pilots to turn on the seatbelt light and make an announce about turbulence so they don't have to do any work. Its a quid pro quo. Pilots feel pressured to oblige because FA's remember who let them be lazy and who didn't when they deadhead or need amenities in flight and vengeful FAs will charge pilots for crew meals among other annoyances. I hope this does not become a thing at DL.

As mentioned upthread, the aviation map from the national weather service is a great resource...if you know what you are looking at. I check that map before every flight and based on that map, I have not had any instances in which I felt that the turbulence excuse was being used to promote laziness. I had a flight not too long ago in which a fellow pax did accuse the crew of using the excuse because we had zero turbulence and FAs were seated for the first two hours of the flight. There was an area of severe turbulence across the Midwest - the type that puts you on the ceiling so we took a very long route and just skirted the area, but most pax were not aware of that. We were close enough to that area that it was not worth the risk in my opinion.