Generally being able to customize the terms of your travel, being able to permanently leave your home country, somewhat being able to choose tax jurisdiction, consular support from multiple sources if things go pearshaped.

Older people probably value choosing favourable healthcare systems too. Nations aren't static entities, I'd doubt you'd find many people willing to bet on a single country's circumstance being exactly the same 30 years from now.

For the wealthy gaining dual/multi citizenship is common across the world and plenty of Western nations sell it off willingly.

https://www.scmp.com/news/world/united-states-canada/article...