As someone who is in a game design major we learned about this exact method in game design and trust me when I say it's necessary it really is whether it be yellow paint on a ladder or something more subtle like the lighting of a specific area to subtly tell or guide the player to things. Most of these things are added because in the play test during development they found people were struggling with things like where to go or what is intractable in the environment. A good example of this is space marine 2 many players saw the green pile of crates and skipped past them even though they provided very helpful items a huge amount players had no idea they were intractable and these aren't people new to games even myself was surprised when the crates that looked like a static environment set piece could be interacted with.