Depending on their severity, addictions, felonies, learning difficulties and health problems (and many other things) could all be legitimate limiters on wealth building.
I'm in the [100k, 200k) range, and I've had to reevaluate my finances. I used to live pretty comfortably on less than half my income. I had no credit card debt, my $50k car was paid off. Student loans were paid off a decade ago. Then, I got married and now have 2 step children. Between moving into a larger place to accommodate the new family and all the costs associated with getting married, moving & furnishing a larger place, I'm just now about to start to get our heads above water. I had to take money out of savings before we could get outflow to be less than inflow.
My prior comment before removed was 5k savings, 11k 401k. I had more, but life events. For me, it's a variety of things. Largely summed up as I bought a house at 25. Had health issues that were in remission, then came back. And have been trying to get above water since.
I know a number of software engineers, who are in it just to pay the bills. As the pay increases so do the responiblities you hold.
There are a significant number of exceptions to this idea. If you dig a deep enough hole (drug problems, felonies, etc) it's hard to just keep a roof over your head.
And sure, "it's their fault", but for a lot of people the die was cast when they were very young.
(Update: I should clarify that this may be a U.S. problem vs a first world problem. The safety net here is abysmal, speaking as someone who has spent way too much time and money helping a friend manage.)