From my own experience (one apprenticeship and 2 years of practical training after university) I can tell you that sometimes even different departments in the same company building work differently, depending on things like work ethic, motivation, skills and personal life.
I might also add that many people VASTLY under- / overestimate what a beginner should be capable of. Some of them just seem to forget how they started and how difficult it is to learn many things at once (because, you know, they have been doing it for years and don't have to think about it anymore... "obviously" you must be a complete moron because you can't do the same thing right now).
Also, helping a newbie is always more work for the beginning. That's a fact, simple as that. In Germany we have a saying along the lines of "Give me an apprentice who only triples my work, and I will kiss your feet."
Everything but polite and constructive criticism is not warranted!
I've been there. Trust me.
Also, this might be inspirational:
I've been drained by people's behaviour before, it is just... painfully numb I guess.