"This stupid idea that poor = lazy/bad is so entrenched in the US society (and was when I was growing up too) that it can ruin your social life from very early on"
If you aren't mentally or physically unable to do something (which is the case in a small percentage of the population), you shouldn't be poor. There are many opportunities in the US. I've been poor, had many poor friends, and now I'm doing much better.
Poor, many times, can be changed, but people aren't willing to change their lifestyles.
Many people have free time after work (if you aren't working, you have even more free time). I chose to learn a skill during that time. Many of my friends, who still aren't going anywhere in life, chose to drink, have fun, and party with their friends. I sacrificed that time (for awhile at least) for my career.
Many people also don't understand delayed gratification. They need to have everything now and as a result, suffer financially.
"least middle class so they would have better social connections later in life"
When you have more money, it becomes difficult to stay friends with people that are consistently poor. Many times because your problems, outlook on life, and hobbies change.