Space researchers have sent many radio signals into outer space over the years with the hope that a distant alien civilization might hear our cries and answer back. Unfortunately, we have yet to hear from anyone.
Astronomers often wonder whether life exists beyond the Earth, but finding a waterlogged exoplanet just like Earth has been a daunting challenge thus far. Experts usually look for traces of water when searching for life, but many agree that a bevy of ocean worlds sport subsurface oceans rather than surface oceans like those found on Earth.
Subsurface oceans would make detecting alien life on other worlds even more challenging, but it might also have implications concerning that what those aliens are capable of. For example, the thick wall of ice and rock separating them from space might muffle our signals or prevent said aliens from achieving space travel.
Alternatively, there's always the chance that aliens want to stay hidden or that they plan to sneak up on us when we least expect it.
Hypothetically, it's entirely possible that advanced alien life forms live beneath the surfaces of subsurface ocean worlds, but there isn't an inkling of evidence to support that theory yet. Perhaps when we study places like Enceladus, Europa, and Titan, we'll achieve a better understanding of what these worlds are like and where to look for them.
Until then, the question about why we haven't heard from aliens yet has no definitive answer. There might, or might not be, alien life elsewhere in the universe.