Probably only a very tiny fraction of planets can sustain life at all.
Of those that can, half or more may only be roughly at our stage of development or less.
Those more developed may simply be uninterested, or may have been "bitten" and pulled back.
Of course, it may be totally impossibe for living creatures to achieve trans-light speeds and survive (if they can be achieved at all.) They may have been on the way here for thousands of years, and will not arrive for thousands more.
Or we may be a singular event in all the universe. I've never seen any proof that we're not. If there is other sentient life, they may think that
they are a singular event in the universe, and may never have bothered to try finding out otherwise.
Or maybe they already have been here, and just don't like us