Why are there so few isthmus on earth?

There are relatively few isthmuses on Earth primarily due to the planet's geological processes and tectonic activity. Most landmasses are separated by water bodies, forming continents and islands, rather than being connected by narrow strips of land. Additionally, isthmuses typically form in specific geological settings where land is uplifted or where erosion has occurred, creating narrow connections. These conditions are not universally present, leading to the limited number of isthmuses globally.