"Poor people are mostly poor because of the decisions they make."
* Drug addiction
Yes, a person can choose to use drugs. Usually the choice is made under intense peer pressure and at a young age. We won't let children under the age of 18 be bound by contracts, but we still stigmatize them with poor choices made when they were often younger than that. Once drug use becomes drug addiction, it is no longer a choice and is excruciatingly hard to break out without external help.
* poor budgeting
Yep, budgeting is important. It's a shame that this isn't given top billing from about grade 4 on. Budgeting isn't just about managing monthly income and expenditure, it's about forecasting, and understanding financial risk management. Unfortunately, at least in the US, the education system is pretty abysmal, and it appears to be difficult to actually get students through school in some parts of the country.
* gambling, alcoholism,, mental illness, etc, etc, etc."
These are actually all tightly linked to the word "illness". Gambling is often a learned behaviour that is linked with poor risk management and financial planning knowledge (see previous section on budgeting). Alcoholism is learned behaviour, that like gambling depends on poor impulse control, and addictive tendencies which are both physical and mental illnesses (or just illnesses once you get past the labelling stigma).
"Hard working people with not vices don't live in the slums and generally can support their basic needs."
Turn on the news, or better yet, read a couple of socio economic studies -- especially ones whose conclusions you find distasteful (it helps break your personal filter). This is flat out false - it is hard to support your basic needs when minimum wages are too low, finding full time work is hard, and there is a glut of skilled professionals who can't find work in their field, so they take up all the entry level jobs.
If you are actually an engineer you should be capable of composing a better comment than what you wrote here simply by thinking it through first.