It is often said that Japanese don't express their honest feelings. This attitude is rooted in their mentality of respecting others and avoiding things that could make others uncomfortable.

For Example: Boss said" let's go out for a drink sometime.
Employee said" Yes, let's do that one of these days. (建前)

Employee's mind: I don't like the idea of going out for a drink with my boss because I have to be careful about what I do and what I say. Maybe I'd better respond vaguely for now. (本音)

本音
One's honest feeling. It is considered inconsiderate to speak one's mind directly.

建前
one's outward stance that changes depending on time, place, occasion, social morality and to whom he or she is talking. Diplomatic remarks are included in tatemae.

So... what is your point?
We all know what is 本音/建前 so you don't have to explain the meaning here.

Are you asking our opinion?
Or you want to know why 本音/建前 exists in Japan?
Or you are just saying that you don't like it?

In any way, I must say that Honne/Tatemae is one of the many things foreigners don't really understand. Japan is a highly group-oriented society and we value Harmony very much.
Of course we all have our own opinions and feelins but we don't say those personal things first. We think about the group first. We think about what it the right thing to do/say as a member of the group. If it doesn't contradict our true feelings, no problem, but if it does, we usually choose the thing we're "supposed to" do/say, which is often called 建前. However we can express our true feelins at a right moment, which is ofen called 本音.

As long as you belong to a group, we all know that there are two kinds of opinions; the opinion as a group and the opinion as an individual. When you are asked our opinion officially, we are supposed to express the opinion from the group side. However of course we know our personal opinion and they are expressed only in an appropriate situation unofficially.

In order to say 建前, you have to know what is expected to do/say depending on the situation. You should read the situation, other people's feelings and what is important in order to do/say for the group (not for yourself). This is one of the things all Japanese adults have to learn to make our society work as a group. Thus you don't understand the idea of 本音/建前, you are considered to be childish, thus you would have hard time to fit into the socity. But most Japanese learn that during the childhood.

I know that it is confusing to foreigners but 本音/建前 is not always a bad thing.

Japanese are group-oriented people and we put group first. Saying 建前 is gesture of harmony, how the society should work and we are willing to sacrifice our personal feelins. Sometimes we do something we don't really want to make the things work smoothly, right?
We do it at a socity level. This is one of the reasons why Japanese society works so well.