Take houses for example, many people buy them not necessarely to live in but as an investment vehicle since the value of their local currency is fallen faster than the house. The more do that the claims they are for that currency when people are selling, plus these people are measuring the house price in that currency. But the most important thing that stengthens the currency is the fact the people are willing to sign their life away on mortgage contracts that will take their years of hard work, time and energy to pay that back. This also strengthens the currency because the debt is denominated in it. There are many other things such as 401k, taxes, stocks, bonds, etf, now the #bitcoin etf