Solar eclipses are not rare. In fact, they happen between two and five times each year.
However, most are partial solar eclipses, which very few make any effort to see. Total solar eclipses — in which all of the sun is blocked by the Moon — happen only once per year and occur in geographically very narrow corridors called a path of totality. These are the events eclipse-chasers travel to experience. In some years they total solar eclipses don't occur at all, so on average they happen every 18 months or so. On average, a total solar eclipse occurs on any one location on Earth every 375 years — southern Illinois experienced totality on August 21, 2017 and will again on April 8, 2024.