Boredom is the worst pain ever described by people who have experienced extremes of it... and the worst extremes (solitary confinement) have proven to be mind-destroying. People do need activity.
I know the typical response will be that people left to their own devices will often engage in useless activity. This is subject to lots of quibbling over definitions and personal values. What you might call "screwing around", for example, often involves some form of exploration for most people, which is not immediately productive but contributes to the growth of a person so they can be more productive later.
We do have a lot of activities available to us now that are completely useless, such as MMOs, where a person can completely rot away while doing nothing useful. But ironically, MMO addiction is directly related to the human need for activity and progress. They're designed to present you with a constant flow of increasing numbers, generating a perception of progress. This taps into the brain's natural mechanisms that provide you with a small but constant feeling of accomplishment, which is physiologically represented by small releases of dopamine in the brain. Those games get a lot of criticism for being repetitive, grinding, unfulfilling... like work... but they're addicting because they're designed to allow people to tap into their natural physiological work-triggered reward mechanism with as little actual effort as possible.
While these things are problems, they're also evidence against the claim that people are lazy. In fact, they're proof of our ingenuity applied to maximizing our return return/investment ratio in regards to fulfilling our natural drive to work. In essence, we've worked really hard over decades of game development to perfect our ability to avoid working hard.