A second citizenship allows to facilitate international travel, avoid dependence and oppression, whether economic or otherwise, from a single government, and to unlock the advantages of certain business-friendly locations.
A 2nd passport is the 1st flag of flag theory because it decreases our reliance on any one government. We begin our journey as a sovereign individual when we are able to live outside the borders of one specific country, now this doesn’t require a 2nd passport- but it does help.
Here are some common reasons why it makes sense to have multiple official travel documents.
Ability to travel visa free
Worse case scenario insurance
Finally – if you are America, an alternative citizenship gives you the right (but not the obligation) to renounce your American citizenship and finally eliminate your worldwide tax obligation. Unless you have a second passport, this is impossible. You are fully in the clutches of one government, and beholden to their oft reckless and negligent international relations.
The US government for instance, instituted a law starting in 2016 that allows the IRS to make a request to the state department to cancel the passport of American citizens traveling abroad. You can read more about how passports can be cancelled by the IRS here.
Compare instant citizenship by investment programs at passports.io.