As far as I know, smoking is banned on all commercial flights now, and I don't think any airlines allow it anymore. The illuminated signs are probably there for safety and to serve as a clear reminder, especially in case of emergencies. Simple stickers might seem like a cheaper option, but having a visible, illuminated sign can make a big difference when you're in a packed cabin.
For those who still want to enjoy something while flying, I recommend checking out alternatives like e-cigarettes. I’ve found some good options at
e-zigaretteria that could be more convenient for travel.