Question

I feel they do it because some people do want to know what's going to happen to see if they want to carry on reading. However I can see how it can spoil it for some if they don't leave a gap to hide it from people

I think there's nothing wrong with spoilers as long as the person at least takes the effort to hide them from plain sight. Some people tend to be too impatient to wait or want to talk about the spoiler with others. Personally, I'm in the neutral with this as I don't really care if someone spoils it or not. Even if someone spoils the story it isn't the end of the world.