[crazygringo]

They were to prevent burn-in before monitor sleep (standby) was invented.

I don't feel like I remember having that in the 90's at all. Not on my PC running Windows 3.1, or on my Mac SE. But maybe I wouldn't use it because the CRT would take a bit of time to power back up?

Does anybody remember when monitor standby mode became widespread both on monitors and computers and OS's? My google-fu is totally failing, maybe I don't know the right search term.

[Dalewyn]

CRT monitors even after the introduction of monitor sleep still took several seconds to get up to full brightness. Better than the several minutes of ye olde CRTs, but still annoying enough to merit screensavers.

[overcast]

Maybe my memory fails me, but I thought for sure our home PC had it. I get the reason for it prior, but I swear that was a pretty early development as the personal computer became more prevalent in the mid 90s at least.

[crazygringo]

I just looked at some Google Image searches and it seems pretty clear that, at least in software, there was "Stand By" mode in Windows 95 both when shutting down and for screen savers, but there wasn't any in Windows 3.1.

So I guess it was a mid-90's thing that it rolled out in software, although obviously you needed to upgrade to 95. No idea if hardware supported already existed or lagged behind though.