Many people live near or on volcanic mountains in the islands of Southeast Asia primarily because volcanic ash provides fertile soil.
The nutrient-rich soils that result from volcanic activity are particularly advantageous for agriculture. This fertility allows for the cultivation of a variety of crops, which is essential in regions where agriculture is a primary source of livelihood. While it's true that many volcanoes are dormant or inactive, the benefits of fertile land often outweigh the potential risks associated with living near volcanoes.
Other factors, such as cultural and historical significance, availability of resources, and access to water, also contribute to the habitation of these areas, but fertility is a key reason.