If their ego is strong, or they are afraid, sharing the truth with them may be grossly misinterpreted.
Your belief in the truth is admirable. Your conviction and faith in it is well placed. And you wish therefore that everyone would simply see this same truth and be set free.
However, this is assuming that people are PERCEIVING CORRECTLY, and that just by sharing truth they will "get it".
People are not perceiving correctly when they are "in need" of help. Therefore if you share truth with them, they will see their own misperceptions in it, will interpret it as an attack (at least at first), and will reject it.
People WANT to be unconscious and asleep. People WANT to be sick. If you try to take that away from them when they aren't ready or willing, or push them too fast, you will just continue to scare the shit out of them.
This is an error I have made many times. Allowing someone to stay in suffering is quite a challenge, especially if they do not want to be helped. It's a challenge to accept them unconditionally regardless of their willingness to change.
If someone is insane and hallucinating and you show them something that is true, they will not see it as it is. They will see what they mis-perceive in it. They will see their ego reflected back. This will frighten them. They will react to this frightening perception by blocking it, making them sick.
Jesus warns us against trying to perform miracles all of the time because, in some cases, the person's reaction to something "miraculous" happening could frighten them even more than the amount of fear you were trying to heal.
This is perhaps also why God doesn't just rush in and scoop everyone up "forceably". Love does not force. It has infinite patience. So we need to learn to be discerning and allowing, letting people have their chosen suffering even if that's all they can accept for now. Slowly and eventually they will come around.
The more you try to help, save, fix, heal, liberate, etc, the more you may be pushing someone into reactions and defenses which are making them sicker.
If you try to shove Course truth down someone's throat when they are unwell or afraid, it may make them even more depressed. Mis-perceptions are the problem, they interfere with communication, they impose a "learning disability", and make it harder to correctly reach someone.
Unless perhaps you are Christ or Holy Spirit and know exactly what is most appropriate. But even then, the person has to have willingness to allow themselves to be helped. If you step away from their help, they will not force it on you.