I don't disagree with your assessment. It is potentially wasteful to have true beginners starting out with high-end instruments as they may not stick with it. I'm not entirely sure that there's a ton of evidence that someone who starts at the higher end is more likely to give up (e.g. my friend has become a very good guitar player, plays regularly at his church and has been at it for 10 years), but it could be true. I think that the extent to which someone stays with music (and has a commitment to it) could be in how much of their disposable income and time they invest in it. This is where it gets relative - more likely the percentage of disposable income vs. the absolute amount of spend.
Ultimately, even if someone starts at the high-end and quits, it may create a good used gear buying opportunity for someone else. I do think that your suggestion is related more how things should be done. My point was more related to how things actually happen. For example, some people's first car is a used beater that they saved a long time to buy, but other people's first car is a new BMW from mom and dad. It probably doesn't make sense for someone to start with a new BMW, and the commitment and investment is definitely greater in the former case. However, there are still a lot of people who start out with a pretty high-end car, and it probably doesn't bother the people who are paying as long as it's within their means.