Very simple. Most people never do Shadow Work and never question their own belief system. So all that they are manifesting 24/7 is the input they received from society and media. At a very slow pace some beliefs within society change and by this those people unconsciously absorb those new beliefs and then slightly switch timelines respectively.
If you are aware that you are manifesting your own reality and do proactive subconscious belief changes within yourself (e.g. with SLR 3.0, Melleable Ego, Soul Continuum and other fields and tools), then you are constantly changing your belief system and by this what you are manifesting. The more consciously you are doing this, the more you can notice the “switching” and the “shifting” (because you are the source of the change, because you are the active driver instead of the passive observing passenger).