That's bec a large percentage of modern people r very very weak in areas like the core and the hamstrings/glutes, both in actual strength, flexibilty and elasticity.
The Pose method of running is structured after how world class runners actually run, esp African-born ones, who have spent their entire formative years living and running in more primitive and rugged conditions. In a greater degree, these ppl have developed higher levels of physical fitness, stability, integrity and coordination due to their more active and rigorous daily routines, like farming, tending cows/sheeps/horses/etc, climbing trees, hunting for food, walking/running to and from school/work, etc.
Modern city dwellers like us, however, spend more time sedentary, and we get around mostly on motor vehicles. We spend little time squatting, climbing, barefooted, etc and so never really developed certain anatomies to their fullest extent. We develop weaker core strength and poorer athletic coordination. Even the more active city dwellers spend relatively less time exercising than more primitive ppl, bec for us exercise is a matter of choice, but for the primitive it is a way of life.
As such, in order to run as our bodies r intended to, we actually need to re-train and develop many body parts.
In addition, whether civilised or primitive, as human beings we all have physical misalignments and imbalances. Most learners of Pose quit bec they can no longer adopt any form of muscular compensation for these imbalances when they run Pose, something that they had been able to do while running their previously 'natural' style. Learning the Pose method demands that one takes the effort to correct one's structural faults so that the chances of injury both in running and other forms of physical activity will be vastly reduced. U also learn faster and more easily.
But being typically modern and therefore impatient, we demand quick fixes that do not exact any price on our part. We pefer to live in denial that the technologised comfort of our daily lives actually have ill effects on our physical well-being as well as athleticism. We want so much for running to be 'fun' and 'natural'and 'recreational' that any suggestion that we have to learn how to do it right sounds blasphemous. So we quit easily and just go for gimmicks, like changing shoes. That way, we can blame the method and not have to change our habits.
So, a re-training of how ppl use their bodies (via drills) and how well those parts function (via strength work) r needed to prepare them for learning to run correctly. Or else we shall spend the rest of our lives going from one kind of crutch to another, while never really learning how to use our bodies as they had been intended to.
So for the original poster, u may or may not wish to learn the Pose method. However, it is still important to explore new ways to train and to utilise yr body. Check for physical imbalances and find out what can be done to sort them out. I'm not saying that footwear do not matter; they do, but this is only part of the problem and we still need to work on other areas. U can try lower profile shoes as well as barefoot running, in limited volumes initially. But this won't cure achilles problems on its own if u have a leg length discrepancy, perform insufficient strength training, have an underdeveloped core, only run and do not do other sports that encourage multi-lateral movement and coordination, run too much beyond yr personal limitations, and often fail to listen to yr body, etc.