I am curious why Stack Network can't count all websites' achievements together. If someone has many stack websites, it will not show all points of a contributor. It sounds that it's a waste of time to level up for other insignificant websites. The question differs from Unify reputation across multiple accounts?. In my opinion, it's strange to bound the site together on the menu but counts achievement separately.
Achievements aren’t synced across all sites.
Achievements show your knowledge so if you know a lot on Site A and not a lot on Site B there’s not really a point as it would be:
Confusing, people thinking what Site you earned it on.
Misleading, people thinking you are an expert on the subject when you’re not.
Unworthy, you feel proud of achievements on a specific site and not just I got this on B because I got it on A. You also didn’t do anything to get that achievement on Site B but just click a button and register.
You can view a list of all accounts including reputation and badges on stackexchange.com and clicking your profile and then accounts.
You will be able to see all accounts the number of different types of badges earned and feel truly proud.