How wage contracts in capitalist economies work

So, a quick summary on how labour markets work: employers post job positions, people apply to those positions and there is a probability that they receive an offer for the job. Sometimes, there is no salary stated in the job advert, in which case when the prospective employee gets offered a job, they can either negotiate their wage, or accept/ reject the wage offered by the employer. In the case where the wage is mentioned in the job advert, the prospective employee accepts/ rejects the job offer (or perhaps there is room to negotiate the wage, depending on the employer). Either way, the entire point of labour markets is that people can sell their skills in exchange for compensation (wage and other benefits etc.).

What people do with their wages, when they accept a job offer is the employee's determination alone, as long as they don't spend their wages on e.g. illegal things, or things which would cause knock-on effects, significant enough to affect other people's/ society's lives in a bad way.

I will take this moment, to point out that academia and being a PhD student receiving a stipend/ scholarship are also types of jobs, because they produce knowledge and provide educational services in exchange for monetary compensation.

Employers are both private, and public. The source of the employer's revenue does not matter, after wages are paid to employees. Wages are still wages, and they belong to private individuals when money changes hands.

An example of spending wages on things which have knock on effects, which are socially bad, is e.g. things that effect health outcomes. Especially in the United States, healthcare access is determined by health insurance status, and health insurance premiums are based on health risk. So anything people do to affect health risk, is a problem for not only themselves but for everyone on their health insurance pool. If it were a problem only for themselves, it wouldn't matter at all what individuals are doing to impact their health risk, as they would be the only ones dealing with the consequences. However, because of insurance, what one person does to impact their health risk, becomes everyone's problem.

Which is why, complaining about people buying things that worsens their health risk is logical. Being frustrated and saying tax dollars shouldn't be spent on social programmes, where individuals are doing things to increase, e.g. health risk, is a valid argument because it effects average insurance premiums. (Yes, I am alluding to preventive health practices, or lack thereof).

If people spend their wages on personal effects, or recreational/ entertainment activities, on average, it is not a cause for concern. Again, unless it badly impacts people other than yourself, which superficial consumption and enjoying sensible recreational activities, typically don't.

If you have a problem with people doing things with their wages that only impacts them, then you might want to do additional inward self-reflection, of why that bothers you so much. Or even, being bothered by people choosing to save instead of spending all of their wages.

If the question is instead to do with, why do only certain people earn wages allowing them to be able to spend on things other than the basics of life, then that is a much much much deeper question.