That’s usually because that’s all they know. With a bit of smarts, lights can do more than just toggle on/off when you go over to the switch. They may appreciate that if they knew.

My most automated light is my dining room/office

• I may walk over and use the switch - but I adjusted the dimming speed so I can walk out of the room as it’s dimming to off
• I may use Alexa/siri/nabu, and that’s the most convenient way to get exact dimming- I also set dimming speed faster
• on weekdays it also turns on at dusk, dims at 9pm and goes off at 9:30 to help me establish better sleeping habits and make the house look lived in when I’m away
• I’m considering ways to have it automatically turn on when I come home at night so I’m not entering a dark house

Do I need those? Of course not, but those are actions my house can take for me, to make things a little nicer