I don't think it feels abandoned. At all. I'm always starting new characters and see the starting planets filled with people all the time. I also see fleet constantly busy and the other planets have many people as well. So I don't get where you are under the impression that this game feels abandoned. Sure, it doesn't have 100 people every square game mile, but it has lots of people.
And let's be honest. Sometimes there can be too MANY people.
It probably has more to do with how static world is rather than actual player count. Since mobs rarely move around and the planets pretty much never change, you can feel pretty alone out there unless you see the occassional player moving around. And that can be pretty rare depending on the planet you're on. On Balmorra there's usually 80 players tops during the weekend, which isn't all that much when you look at the size of the gaming area.
But personally I like it that way. I actually go out of my way to avoid other players and try to play when I think there'll be less people since they tend to ruin my cutscenes by drawing their lightsabers, running and jumping around, etc.
Still, I think they could change a few things here and there to make the worlds seem more "alive" even when there aren't other players around. Maybe have certain creatures attack each other to simulate "hunting" or have mobs move around more. Add some small weather effects like rain in certain areas. I think there's already water rising from the waterfall in Dromund Kaas, more little stuff like that. Fog appearing at random times maybe. Etc.
(I think they added smoke to the chimneys at the balmorran arms factory - that makes it seem like the factories actually in use. Stuff like that).