Just like getting a regular oil change for your car or truck, your home's pipes and water system also need regular maintenance and check-ups to ensure they're running right. This is why plumbers also offer upkeep services to test your entire plumbing system on a monthly or biannual basis to catch any issues with your pipes before they become an emergency.
Sometimes a faucet leak can be stopped by replacing the rubber washer at the end of a faucet stem or cartridge. This is a more common repair on older fixtures when things were built to last and designed to be able to be maintained. Other times the whole stem or cartridge needs replacement or the bibb seat deeper back into the fixture needs replacement. That leads to matching up the right components and often times making a trip to the hardware store or plumbing supply house necessary due to the many varieties, makes and models of faucets. My advice is to make sure your Plumber has faucet repair kit on their truck before having them come out to assess the issue.