would personally prefer a more proactive approach where the signs are turned on whenever the pilot judges that he is likely to experience turbulence
It’s a fine sentiment but rather difficult to action in real life. After 20k+ hours flying, I have come to realise that you can get turbulence just about anywhere, forecast or unforecast. If you use the criterion “it
might be bumpy ahead” to turn the seat belt signs on, how are you logically going to turn them off again?
All said and done, what are you really trying to do with the seat signs? I’d have said prevent injury. How often do you fly through something that would cause that to an unsecured passenger? It happens but (for me) it’s pretty infrequent. As others have said, if the signs are on for long enough in smooth air, people will eventually get up anyway as they assume you’ve forgotten to turn them off.
In my initial welcome I include instructions to wear the belt at all times when seated and to sit down and belt up as soon as the sign comes on. I will preempt turbulence if it is almost assured (pilot/ATC reports, clouds of certain types, etc.) but generally will respond when it goes over a certain level. Sometimes you get hours of annoying light clear air turbulence which never develops into anything more malign (tropical regions are good for this) and I’m happy to keep the signs off, reserving them for when I feel they are actually necessary.
At the end I suppose it boils down to whether you are more interested in preventing harm by trying to understand human nature or just attempting to cover your posterior. The ultimate expression is to leave the signs on all the flight “just in case” but this will lead to people being out of their seats right at the moment when they really shouldn’t be...