The thing is, your stand is in contradiction with your characterization in the initial post of losing 5 pounds a month as a "healthy rate". That implies 60 pounds a year. If people are taking a decade to lose weight, that implies they were like 700+ pounds. I've read of such cases, but they certainly aren't common. So either you don't think losing 5 pounds a month is healthy, and that people only should be losing 5 pounds a year or something, or people do in fact lose faster than they gain, except for the exceptional cases gaining say 150+ in 3-5 years.
In reality, most people simply don't truly commit to the permanent healthy lifestyle, and regain weight. Or those who take a super extended time to gradually slim down are oscillating between periods where they are sticking to the healthier regime with periods where they act as they did before and lose some of their progress. It's not that it really takes that long to take the weight off, it's more that people have different ability to stick with their program, and maybe difficulty finding a program that is truly sustainable for that individual.
My stance is:
- figure out how you want to adjust your eating/lifestyle, to something that is healthier and you think you can maintain indefinitely
- try to lose weight at a reasonable clip somewhere between 3-8 pounds a month depending on where you are starting from, pace will naturally slow as you drop
- at some point you will reach your weight goal and find a eating/activity balance to maintain equilibrium
- then stay on your plan and work on maintaining at this level thereafter, adjusting as needed.
It's still a lifetime thing, long process, but I don't see why one should only try to lose like one tenth of a pound per week. Lose weight faster than that, most people ought to be able to get to a weight goal within 1-3 years, then the long (forever) time is remaining in maintenance.