I answered it, Yan.
He speaks to all. Only some can hear Him. The reasons for that vary. God does not force himself upon us. Those people who think He should just announce himself like he did at Sinai with Moses seem not to recall that the people were terrified and did not want to hear him. Also, some don't want to hear.
(And I don't mean that they don't want to hear their god talking to them. They don't want to hear THE God talking to them, through His Son or not. Because what God would say to them would not be what they want to hear. For some, it would be like the pharisees that Christ rebuked. Some people want to go their own way, even though some have convinced themselves that what they want is also what God wants. This brings us to those who cannot hear, because they are listening to something or someone else. Therefore, they cannot recognize God at all. Only the lie.)
Why does He speak in spirit, rather than in some loud booming voice (other than the fear and ensuing panic that would follow)? Because He IS spirit. He did send Christ, his image, to us. So we had the physical voice and body to hear as well. But we are also spirit within, and I think we have to learn this and remember this. We have to move past the limitations of the flesh.
However, all that being said... if you know the golden rule (do unto others as you would have them do unto you); then He has communicated to you in a way that you can understand. You may not credit it to Him, but you still heard it.
Peace,
Tammy