So why do we need to show off? because we are seeking external validation, of course. And why do we need the validation, because we don't value ourselves. It is always like if we don't get that job, that apartment(Read so-called family life), or that car, etc, we have not achieved anything in life. We attach our peace of mind to our desires. As a result, we are becoming so materialistic, a salve of consumerism. It is easy for manipulative masters to control us by showing us the carrot of growth, and success(the name varies according to the domain in discussion). The intended outcome, peace of mind is always out of our reach.
Now there is another category of people, the so-called knowledgeable, those who are worried about their status in this dystopian society, so they show off to keep themselves relevant in their social circles. Previously politicians would maintain a low profile, at least in the northeastern side of India. Now because of this, corruption has reached a threshold level. So-called religious people are also not untouched by this trend, after all, they are also part of this society. Their pseudo-spirituality has made them live a luxurious life so that they can attract more disciples, resulting in more tax-free donations (income).
The life is to live, not just to survive. Living life on our own terms is difficult, as society does not permit it. Society wants human resources to run the system smoothly for their masters, especially those who have control over natural resources, the corporations. We need to understand that our boasting would not take us anywhere. To know ourselves fully, to be aware of our true nature, and to seek the ultimate truth can only help us to achieve peace of mind.