Unless you are taking the cave/paleo thingy way to seriously, you´ll have heard that it´s a good idea to limit exposure to light (especially blue light) before going to bed. Then again, it is estimated that 90% of the (American) population use some type of electronics before bedtime, so it might just (once again!) come down to plain old stupidity and/or a disinterest in ones own health.
People tend to focus loads on nutrition and exercise, but fail to recognise that poor sleep may severely diminish the positive effects of doing right in these two arenas.
The short abstract below is indeed worth reading, as it sums up a very interesting study examining the effects of looking at your electronic devices before bedtime.
The use of light-emitting electronic devices for reading, communication, and entertainment has greatly increased recently. We found that the use of these devices before bedtime prolongs the time it takes to fall asleep, delays the circadian clock, suppresses levels of the sleep-promoting hormone melatonin, reduces the amount and delays the timing of REM sleep, and reduces alertness the following morning. Use of light-emitting devices immediately before bedtime also increases alertness at that time, which may lead users to delay bedtime at home. Overall, we found that the use of portable light-emitting devices immediately before bedtime has biological effects that may perpetuate sleep deficiency and disrupt circadian rhythms, both of which can have adverse impacts on performance, health, and safety.
Chang et al., 2015