I guess to each his own then. Personally I don't like always checking on my seedlings to see if I need to turn the light on or not. I just turn the light on and they do the rest. There is no damage done if you use lights or not in-fact I still believe it's better because it can help to warm the soil or grow medium. Seeds do like warmer temperatures and a seedling mat only heats the bottom and not the top of the soil where the seed is.

Peace all.