Water is also really common (if not usually liquid), so you might expect that a good fraction of all the life in the universe would use water. Why worry about looking for exotic life in galactic nebulas (or whatever) when we aren't even sure how to detect it. Working out a way to detect watery life is way easier, and if there's a nearbyish exoplanet with a rocky Earthesque planet with water then we absolutely should look there first.
Water is awesome in that is a universal solvent. It's plausible life could form around a different universal solvent, but to date, we don't have any evidence of it happening.