My answer to the title question is both. A worthless life is the cause of reckless, and ruthless mind you, behaviors.

Why is their life worthless (mass perception at any rate)? Many reasons.

Who says life is worth anything?

The 'West' has Judeo-Christianity, Buddhism, Islam, Hinduism, Taoism (Taiwan, HK, USA...etc.) All teach the value of life.

What does mainland china have?

a. Communism, to be specific, mainland chinese version of communism, CCP's version. So, what does CCP teach? Read/hear PRC's national anthem. In the middle is the sentence, "we carry our enemies' bomb into their camp". And who are the enemies? The evil, corrupted "West". It is a we against them all mentality. What does that remind you of? For me, terrorism, 911, bombs, ....etc. Extremism.

b. Demand and Supply. 1.3+ billion population (reliable sources say it is a gross underestimation). AnyTHING mass produced is cheap. You say, but they are not THINGS, right? Sure. But to who? Back to the previous points, absence of religions and CCP.

c. Cultural 'Revolution'. This is also something they have. Traditional chinese values & philosophies wiped clean, replaced by the Mao idol-worship, or cult. Entire country. Estimated 5-8 million killedfor many reasons, western thoughts, feudal thoughts, possession of western objects, ....etc. Who killed them all? You are looking at them everyday, those who are now in their fifties and up. They tasted their first human blood in their teens, landlords', scholars', professors' , businessmen/women's, their own parents', blood.Consequences, legally, none. Consequences for you, me, and the rest of the world? HUGE. Aren't we experiencing it first hand, my friend? Don't we know it all?

If you were there and you kicked and hammered hundreds of people to death with your foot, bare hands, wooden planks, mentally, emotionally, physically torture them until they commit suicide ...etc. and you were told you did the right thing, would you respect life for the rest of your life? To see live video footage of the cultural 'revolution', go to Youtube.

How old is this CCP administration, the so-called 'china' you see today? 66 years old, since 1949. Very important to keep in mind. It has, strictly speaking, NOTHING to with CHINA. THEY rejected it. Their calling themselves chinese doesn't mean chinese all over the world agree they are. In fact, many don't agree. Guess why chinese all over the world address this new communist breed as mainlanders? Ask HongKongers, Taiwanese, Singaporean Chinese, Malaysian Chinese, .... why....

Is it so that their family can make a payoff after they bite the dust?

Maybe, probably NOT the prime reason. The prime ones are above. 18 committed suicide a few years ago, hanging themselves, jumping off the roof, Foxconn incident. One husband jump off the (5th/6th?) floor of a shopping center in the middle of an arguement with his wife, who bought and bought and bought, asking him to to carry the 'trophies'. (echinacities reported this). Another young guy jumped off a long distance bus (and killed himself) when the bus driver refused to stop the bus for him to take a leak. (also reported by echinacities)

Or am I just biased?