Mamasperspective - I do think it depends on how you wash it, your own unique hair, the products you use (or don't use), sun exposure and the life you live.
Two people I know have "not very nice" hair and don't wash it very often. I do wash mine every day and it's remarkably soft and shiny (so says my hairdresser). I am pretty careful with my hair though as I swim regularly and am aware this is potentially damaging.
The correlation is not necessarily causation.