I can basically single pull every zone in PL. Even before the zone level restrictions in PL, i could twink a character, and solo a much higher level zone by single pulling. eg. Leveling a 30 twink in Oasis. I wouldn't even need to buy healing potions, since they would drop often enough in the higher zones.

It seems that SL is intentionally built to prevent this. In fact, some zones in SL start with a swarm of bugs that cannot be pulled separately.

Is this because STS doesn't like people soloing? Or, is it a way to encourage people to buy potions with plat?

Once I hit 26 with one character in SL, I think I will spend most of my time in PL. I play PL when i have to wait for something, or take little breaks from working or studying, or during TV commercials. I can't be that casual playing a game if I'm forced to group and pay attention the entire level.