Because the price you offer for your time influences the perception of the value of time for everyone around you.
Its why minimum wage exists at all. Without it, the most desperate depress wages to the absolute edge of starvation and destitution. It is not, and has never been, and never will be an answer to poverty, but it is a promise by the government that your time can never be valued at less than an absolute floor they set.
Because nature and reality are cruel. For many people, in many circumstances, their time is practically worthless. Minimum wage has a carrying effect on the economic baseline - by having minimum wage workers, there exists industry to meet their extraordinarily limited means. Its the old Ford adage that he need pay his workers enough to afford his cars lest he have no market to sell to.
This matters to state level actors the same way opiates in the US matter. If isolated, rare, instances of irrationality reign and someone ends up dead from a drug overdose that is a manageable risk for the freedom granted in return. But when millions are addicted, tens of thousands are dead, and whole communities are collapsing from it the individual choices that led people to drug addiction are a consequence to the whole of society.
It doesn't even need be in that large a scale. If your brother is a drunk he will by nature he less productive and stable in his life, more prone to disease and illness, and often fall upon his family for support because he cannot support himself due to his own choices. You can then of course choose to not help him, but for those that do their now deflated resources from supporting their drunk brother depress their participation in markets they would have had more voice in. It takes only one bad apple to ruin a family, a bushel to destroy a community, and an orchard can ravage whole counties.
Its why anyone contemplating suicide is told its a selfish way out. Because you make the choice, but everyone else gets to deal with the consequences. Almost nothing you do is wholly restricted to yourself alone - everything has consequences, and society at all is built on a foundation of trading personal liberty for freedom from others liberties.