It is not the case that locals don't marry foreigners in all countries, including Germany. Marriage practices vary significantly from one country to another, and they are influenced by cultural, legal, social, and economic factors. In many countries, it is quite common for locals to marry foreigners, and intercultural marriages are increasingly accepted and prevalent in today's globalized world.
In Germany, like in many other countries, intercultural marriages are also common. People from different cultural backgrounds may meet, fall in love, and marry in Germany as they would in many other places around the world.
It is essential to avoid generalizations when it comes to marriage practices in different countries, as there are always exceptions and individual preferences that may differ from the general trends.