a) Old LCD monitors were pretty terrible. They were extremely slow to update and could only be viewed at certain angles. Thus the only use for them was in laptops, where people were willing to sacrifice these things for portability.
b) Your PC’s CRT is old. Old TVs took a couple seconds to warm up as well.
Either you or someone else did in the last few days.
Not really. TV sets in the 70’s featured an instant on feature. As soon as you pushed the button the picture came on instantly. Modern TV sets don’t have this feature, probably because it wastes electricity by keeping the picture tube warmed up constantly.