“Most of the luxuries and many of the so-called comforts of life, are not only indispensable, but positive hindrances to the elevation of mankind.”
~ Henry David Thoreau
Hikers are no different from anyone else – we are creatures of habit. Favourite pack, favourite tent, favourite old boots, etc.
There is no denying that familiarity brings with it a certain sense of security. However, if I have to choose between familiarity and a drastically lighter pack weight (without compromising safety or performance), I will go with the latter every single time.
There are a number of reasons, however the big ones are quite simply comfort, health and enjoyment. It is better for both your body, which is less likely to incur stress related injuries, and also your mind, which is likely to be less distracted than it would be under the burden of a heavy load.