The fact they're coming the US literally means its economy needs them.
Of course we could all wax philosophical and say "Nobody needs a Frappuccino every other day, we just want it," but then nobody needs to live in a prosperous economy anyway.
Classical economics would argue that higher population tends to increase productivity (economies of scale and specialization) while lowering wages, increasing land value, and improving returns on capital. Free trade has a very similar effect. You can find this analysis in all standard texts (Smith, Riccardo, etc) and even progressive works such as Progress and Poverty by Henry George.
Different groups are free to have different opinions of this tradeoff. Big landowners benefit immensely while working class renters only suffer.
Not necessarily. As just one example, it could mean one of their family immigrated for a well paying job, and now they want their parents, or other family, to join them and they don’t have skills in a high paying industry.
The presence of low income wage earners does not, by force of nature nor economics, require them.
Having said that, I tend to against minimum wage policy.