Happy to have my flawed thinking corrected - can you share the examples?

I likely am thinking of a narrow set of "regular businesses" - what came to mind were corner shops, hairdresses, bars or restaurants etc. Even in those cases there are obviously large successful busniesses that do have competitive advantages - but I suspect they mostly get erroded away by competition rather than the business being able to sustain them, and high margins. I would love some counter examples though!