Is there an underlying reason why this happens time and time again or do people here just simply not understand the meaning of a "good job"?
Either you have bad luck or bad attitude when looking for a service.
Another mystery is being seriously underpaid, for many works like pavements etc. people aren't paid enough or aren't paid in time, so they loose the motivation.
With services like plumbers - they are very popular and in fact I often hear the best plumbers, builders etc. are booked months ahead, so that it's usually the most crappy ones who are ready to come when you call and they usually offer lower prices. Best thing to do is to ask around if somebody knows a good, trusted worker. It's just like with a dentist or hairdresser.
If you have a feeling that a worker you hired isn't doing a good job, you have to be firm or just kick them out straight away. I sometimes meet a 'I can't do this today, I forgot/run out of ...' story, then I just have to be firm and logical and suddenly they can do it. I don't know if those people do it for some reason or out of sheer stupidity, but they remind me of big babies. How can anyone go to work of this kind without preparing tools and materials?
Good workers exist, but it's harder to get them as they have plenty of work, as I mentioned.
And anyway, I don't think it's a Polish problem. From what I know it's a problem in most places. A lot of people have a bad attitude towards work, also often it works both way, people try to abuse each other and in the end everybody becomes sly and untrustworthy.