Why resident areas are not popular?

[Harmonea]

I mean, you've answered your own question, have you not?

And it sucks cuz I feel like Im the only living person in my ward :C

You are one of those people who need to have other people around all the time. People like you don't like to hang out in empty places, so they... don't.

People who aren't so extroverted might be more inclined to hang out in the wards, but we will also, by our natures, avoid socializing.

You'd likely see a little more activity if there were fewer MBs and bells, but SE has gone for convenience and quiet over the creation of hub areas. You never have to stray far from your house, so unless your immediate neighbors (1) are online at the same time as you, (2) idle during their playtime at the same time as you, e.g. no queues, raids, PFs, hunts, etc, and (3) idle at (but not inside) their houses when they play... It's natural not to see anyone.