The answer to 'why do I have silverfish' is that silverfish are common household pests that are attracted to damp, humid environments and feed on things like paper, books, clothing, and other organic materials. They are often found in bathrooms, kitchens, and other areas with high moisture levels.
Silverfish can be a nuisance, as they can damage household items, and their presence may indicate a larger moisture or humidity problem in your home. To get rid of silverfish, you'll need to identify and eliminate the sources of moisture and food that are attracting them, as well as use traps or insecticides to control the population.