It depends on what you're using the screen for - but in general they're used for changing settings, reviewing framing and exposure, etc. I think they can also b

It depends on what you're using the screen for - but in general they're used for changing settings, reviewing framing and exposure, etc. I think they can also be useful for previewing long exposure settings. Even on very expensive cameras you're going to struggle to use them to do detailed assessment of photos. That said you can absolutely buy hoods for them - though they are generally aimed at people using them for video.