Because it’s the same as being proud you rolled well on a craps table, or got dealt the best possible hand in poker. It was all chance. Nothing wrong with celebrating a cultures achievements. But don’t take pride in the accomplishments of those who came before you, you didn’t make those great things happen. Just like you bare no shame in any thing awful your culture/country/ancestors may have done in history.

If you need the feeling of pride in something do something great yourself. Don’t rely on those who came before you.