They are hiding from us.
Stephen Hawking used to believe that extraterrestrials would have the power to destroy humankind if they ever were to find us, so it would probably be a great idea to stop searching for them.
However, it’s still a chance that they might think the same. Maybe aliens believe we’re going to destroy them, this is why they choose to stay hidden. If they’re as advance as we assume they are, they could use all the technology to build an impressive orbital structure (like a Dyson sphere) to make their planet impossible to detect.
Or maybe they’re using high-powered lasers to create a camouflage that will prevent their planet from being detected by telescopic instruments.
Make sure to also check: Edward Snowden Investigated If the CIA Has Secret Information About Aliens.
Next, there could be a very good reason why we are being kept in the dark…..