However, I think the primary determinant is an inherent trait of people; yet anyone's environment can energize them or demotivate them depending on the person/environment combo.
From what I've seen, people who are engaging in activities that are reinforcing of their core strengths are usually energized as hell, because whatever it is they are doing is re-inforcing, it is a source of positive energy flow, because they are doing something well, and likely being rewarded for it, either via money, recognition, achievement of something they believe in, etc.
I like being productive.
I like being able to have an effect on my environment.
For some reason it is extremely awesome and cool and desirable to me to be able to premeditate a change in my environment, predict what steps need to be taken accomplish the transform, test out my theory IRL, and if I'm able to pull it off - for some reason it's just fun as hell. For lack of a better term, I "use my powers for good" - I don't try to make freaky bad shit happen.
When things got really bad for whatever reason, and I was younger, going batshit wild seemed like a great way to neutralize the pain, and later in life (much later, actually) I experienced my first bout of depression.
Luckily, I snap out of depression fairly quickly, in fact freakishly quickly in some cases, but I believe it is because I am able to look myself in the face and be as candid and honest as I am with others about what is fucked up in my life and what I need to do to fix it. Then it's just a matter of going through the steps to start digging my up to my usual upbeat positivity. But yes, I've had some dark nasty moments too, and they suck.
From what I can tell, (1) some people are OK with their environment as it is and doing what they must without mixing up a whole lot else, which there is nothing wrong with IMHO, (2) there are some folks who are for one reason or another truly apathetic and kind of zoned out/disconnected from what I can tell, but they are by no means a majority so far as folks I have met, (3) others still might simply have a high threshold for engaging in things and thus kind of on autopilot unless compelled to react otherwise - some people are simply consumed by what is going on in their lives, whether they appear busy or not - I totally get that, (4) at any given point in time there are folks who are depressed and thus less active than they would be otherwise - been there done that, and (5) There's the busy folks like us.
Thank goodness there are so many different types of people, likfe would be boring otherwise.
ADHD = Yes
Hypomanic/Manic states = Yes
Overproductive adrenal glands = Yes
Excessive neurotic energy = Yes
Massive hormonal fluctation = Yes
Assertive types = Yes
People with Natural Leadership Skills = Yes
People dedicated to a cause = Yes
People massively in love = Hell Yes
People high on life = Yes
Factors that would increase the "busy-ness" of a person, IMO, include:
Wealthy = has time and resources to be very busy doing whatever they want, when they want
Short on time in a place they love = going to do as much as possible before leaving
New to an area and thrilled about it = busy exploring the wonders of their new environment
Just hatched out of a bad, stressful phase of life and making up for lost time = Yes