They are simply categories that are defined, so they exist by definition. But they have poor predictive power. From wikipedia:
Though the MBTI resembles some psychological theories, it is generally classified as pseudoscience, especially as pertains to its supposed predictive abilities. The indicator exhibits significant scientific (psychometric) deficiencies, notably including poor validity (i.e. not measuring what it purports to measure, not having predictive power or not having items that can be generalized), poor reliability (giving different results for the same person on different occasions), measuring categories that are not independent (some dichotomous traits have been noted to correlate with each other), and not being comprehensive (due to missing neuroticism). The four scales used in the MBTI have some correlation with four of the Big Five personality traits, which are a more commonly accepted framework
EDIT: My theory is that Myers-Briggs is more popular among laypeople than Big5 precisely because it's less scientific. People feel like their Myers-Briggs type tells them something non-obvious about themselves. Big5 is so straightforward that it doesn't tell them anything they didn't know before.
By exist I am referring to the validity of the binary measurements. If I ask you where you generally sit on the binary scale of awake and asleep you couldn’t give a definitive answer because it changes depending on the circumstances. It’s a meaningless measurement (as alluded to in your copy paste). I get the same from MBTI.
> My theory is that Myers-Briggs is more popular among laypeople than Big5 precisely because it's less scientific.
My theory is that it is more popular not directly because it is less scientific, though for a closely related reason--because its so heavily marketed by the private firm behind it and their army of certified consultants, which has created lot of visibility (much of which is at least one step removed from the marketing, so that people are often not directly aware of the marketing.)
I think you have quite a limited view of science if you think it can only tell you obvious things. My view is that Myers-Briggs is less popular with scientists/academics than Big5 because they haven't worked out how to measure it accurately yet.
Though the MBTI resembles some psychological theories, it is generally classified as pseudoscience, especially as pertains to its supposed predictive abilities. The indicator exhibits significant scientific (psychometric) deficiencies, notably including poor validity (i.e. not measuring what it purports to measure, not having predictive power or not having items that can be generalized), poor reliability (giving different results for the same person on different occasions), measuring categories that are not independent (some dichotomous traits have been noted to correlate with each other), and not being comprehensive (due to missing neuroticism). The four scales used in the MBTI have some correlation with four of the Big Five personality traits, which are a more commonly accepted framework
https://en.wikipedia.org/wiki/Myers%E2%80%93Briggs_Type_Indi...
EDIT: My theory is that Myers-Briggs is more popular among laypeople than Big5 precisely because it's less scientific. People feel like their Myers-Briggs type tells them something non-obvious about themselves. Big5 is so straightforward that it doesn't tell them anything they didn't know before.