Certain things can make people fail to pay attention to you while speaking to them.
Firstly, we can have a situation where, due to external distractions, people have difficulties paying attention to you while you are speaking to them. The external distractions can be things like noise, things like stuff happening around you, a stench near where you are addressing the people, heat, coldness and so on. They are mostly things that hit the people as sensations from outside.
Secondly, we can have a situation where, due to internal distractions, people have difficulties paying attention to you while you are speaking to them. Here, we are looking at things going on in their minds, their worries, their anxieties, their fears, their hopes, hunger, pain, thirst and so on.
Thirdly, we can have yet another situation where, due to the manner in which you present yourself, or the manner in which you present your message, people are unable to pay attention to you. If, for instance, you don’t have a ‘presence’ people may be unable to connect to you: leading to a situation where they are in turn unable to pay attention to you as you speak to them. It could also be a scenario where the folks simply don’t understand what you are saying, and where they therefore simply decide to (in a way of speaking) switch off.