Why are we all alone in the milkyway.?

There's a small chance that we're all alone in the Milky Way, but there's no chance that we're all alone in the milkyway.

we dont know yet if we are

are we means we havent found some one yet ..

We don't know whether we are or not.  My suspicion is that there are plenty of worlds with microbial life and very few with complex life, partly due to natural disasters such as gamma ray bursts and asteroid strikes, and partly because the steps leading to complex life are cumulatively improbable.

We don't know. But it is likely that we are not alone. There are trillions of planets. 

The aliens are waiting for civilization to appear on Earth

Who sez we ARE?

The aliens don't like your shotgun aiming, DICK.

maybe we aren't, but the distance makes it almost impossible to communicate with them. Even if a radiosignal were strong enough, it would take years to cross the distance, if not millennia or thousands of millennia

We don't know that we are... there *might* be other civilizations out there, and we simply haven't detected them as yet.  We can't say we're alone - and, we can't say there are other beings out there... we simply don't have any evidence either way...