If the first machines which had segmentation existed in the early '60s, why did it take so long to discover that memory segmentation is an anti-feature? AFAIK

If the first machines which had segmentation existed in the early '60s, why did it take so long to discover that memory segmentation is an anti-feature? AFAIK segments were put in the 386 because Intel thought people would like them, but they didn't. Now segmentation only exists on x86 hardware for backward compatibility, and all modern OS's essentially disable segmentation in software (basically putting all of memory into a single segment) and using paging to implement process isolation, no-write / no-execute, shared memory, and the like. I'm not talking about 8086 / 8088 style segmentation, which was a different beast, a somewhat reasonable way to allow a 16-bit processor to access more than 64k of memory.