I did the short course to get into this industry and I think the short courses probably are bad for the trade but, when I finished the the course I didn't think I would be able to earn 40k a year, I knew I had loads to learn, I knew I would be slow, I knew I'd not make much money at first, and I think if I'm honest I only thought I had about a 50% chance of succeeding. Because of all these factors I started by doing the friends and family's etc and I armed myself with all the knowledge I could, I would sit reading this forum for hours learning new things, tricks of the trade! I start my 5th year in January and touch wood , I'm going from strength to strength. I'm never out of work, mainly recommendations and other trades.
I don't think these courses arm people with enough info though on problems you come across, eg, uneven walls, floors etc.
But, you have to be a fool to think you can just walk into a new trade and be quality after a couple of weeks training, and, I'm guessing not many carry on after a month or 2. I was made redundant which made me more determined to do it right. I know I'm still learning but I reckon there is guys out there who have been tiling 20+ years (not on this forum) who do crap jobs because their not re educating themselves, the trade has moved forward from the days of 6x6 ceramics and some of these guys might benefit from a short course.