Because: THERE. ARE. NOT. ENOUGH. JOBS.
* The economy crashed a while ago. We still haven't recovered all the jobs we lost, by either absolute or percentage.
* Increased automation and efficiency is slowly removing those jobs you just described. Exec, a YCombinator app, makes a more efficient and automated solution to craigslist cleaning jobs. This is happening in every sector in this country. These changes ELIMINATE JOBS, these jobs will never come back. And the jobs they create do not replace the ones they removed, not in quantity, or in aggregate tax quality (i.e. one well paid programmer does not replace the amount of tax revenue from 4 people splitting the same salary. Let alone the fact that executives often take a cut of that increased productivity for themselves. Let alone the fact that it puts more load on welfare for the 3 lost jobs).
* Every single one of those jobs you just listed likely requires a number of things in today's saturated jobs market: High-school or college education (too many people, not enough jobs, means overqualified hiring requirements), a permanent address (hard when you are homeless), a certain appearance (hard when you are poor, without a place to live or bathe), some sort of experience (hard to get in this job market, especially when under educated, in poor health [mental or physical], and every other reason here), transport to and from work (or even for the work), ect.
I think you need to take a step back and look at the whole picture, it's a dire one.