When did network television start running all night?

Question

Does anyone know approximately when network television started running around the clock instead of going off the air at night?Thanks in advance!

Answer 1

When cable TV became more popular, and people started working odd shifts at work.

Until then, they had no competition, and had no reason to.

Also, advertisers didn't think it was worth it to advertise in the wee hours of the morning, so that's why stuff like ginsu knives and chia pets became so popular - commercials were so much cheaper at those times. Now we have more "normal" commercials at those times...