I know this already has an accepted answer, but there's another option, besides all the other suggested:
Capitalism
Those who call upon me do so to be content, but while I am here, they are not content, and will not be until I am no longer there.
Business and sales people try to sell their product(s) or services in an attempt to gain money to be content with their lifestyle. Many are never content with enough stuff and will continue to not be content until they are either dead or retired.
They call me always because they want to forcibly compel someone to obey, yet the other also calls upon me to forcibly compel the other to obey.
Business people tend to use capitalism as a force of nature to get people to buy from them and only them. They will also claim that only capitalism can work for an economy and that no type of socialism or other economic system will ever work.
I am always somewhere.
There's always someone trying to sell something. Whether it's a big box store, a government selling weapons, or a child trying to sell baked goods for a school trip, capitalism is always there. At least it seems that way.
I am always changing, yet not changing at all.
The way capitalism works and is defined doesn't really change, but because of how it works and is defined, it's almost never used the same way twice.
People are afraid of me.
People are afraid of capitalism, because it can cause high prices, can create an artificial need for a product, can easily create junk/useless/worthless/fad products, creates severe economic gaps between people, and can often create unhealthy competition.
Some people love me.
Business people often love the competition, price wars, and money that capitalism generates.
Others adore me.
Investors adore capitalism, since they can get rich off someone else's work.
Some dedicate their lives to me.
Many people dedicate their lives to selling products, while some people dedicate their lives to consuming products. Others dedicate their lives to producing new products for sale.
Some come to me, others run away from me.
There are plenty of people who come to a capitalist country to get away from pre-industrial countries or because they think their product will make them rich. Others flee due to capitalism making them poor, whether it's moving to another country or, for example, living off the land in the mountains.
I am always here because of a dispute, although sometimes I may drag others into it because of practical convenience.
Capitalism can work to settle the dispute of the price of something. Is a cell phone worth a cow, 3 goats, 15 chickens, or 100 rutabagas? Other's get dragged into the conversation to help mediate the price negotiation.
I am considered a disease, a terror, a gruesome act, an art, a theory or an adventure based on who you ask. They even may say that everything in this list applies to me.
Depending on who you ask, capitalism might be the best thing that's ever happened or it could be the worst. It's definitely helped in some ways to push the industrial revolution, but it's also created a huge unemployed and homeless population. Capitalism is also a theory of how an economy can work.
I am associated with suffering and death, though this is not absolute.
Because there are still people who are unemployed, not selling something, under-paid, and more, capitalism still causes people to be under fed, lacking housing, depressed, suicidal, lacking basic medical care or under medicated, and more. Some of these things happening to the point where people die. Fortunately it's not taken to these extremes most of the time. Many people do live normal lives, even if it's not as comfortable as they want it to be, and for successful people, it makes their lives very comfortable and wealthy.
To be fair, you could consider a similar answer for
Socialism
But that would only apply to the extreme version of it, and not the modern versions.
