I actually did understand what you meant, I probably didn't word my reply the correct way.I don't think I ever implied that someone should buy a machine to maybe " follow a dream". What I said was that you buy it cause it can do more and make your workflow faster and easier and IF, IF!! It makes you inclined to try out other things that weren't possible to you before due to horsepower of your previous machines then that would just be a plus. Obviously if your needs are basic and you are just web browsing and word processing then a $2500 MBP isn't necessary and I don't think I ever suggested it was to those type of users. But if you even have a remote interest in video or photo editing, gaming, etc then you should definitely spend a little more for the 15" and not limit yourself.
I can understand and respect the point of view you have, and for some people that is true. Having the extra power and options is a plus and would allow more people to explore the possibilities that you can do with a more powerful 15" computer. But in general most people have a set idea of what their needs are and buy based on their immediate needs within the foreseeable future, as with most other major purchases in life (house, car... wait, since when did MacBooks get expensive enough to fall in with these categories???? LOL).
But in all seriousness, I personally do photo editing on my 13" MacBook Pro. Do I miss the larger screen size of the 15", sure. But ultimately the 13" is more than powerful enough, and I have the option to connect my external monitors should I need it. Many of the things you mentioned as reasons to buy a higher end 15" MBP can be done on a 13" MBP, albeit the processing might be slightly slower.
Ultimately each person should evaluate what their needs are, and what those needs will be in 5 years. If they have an interest in those things you listed, then sure, consider the bigger more decked out machines, but I still think it's a mistake buying a machine for the possible "ifs" that you may or may not truly use down the road.