[dylukes]

Small quibble: converting a measure to a z-score requires an assumption of normality and that you're considering a population.

For a sample the equivalent is the t-statistic, which indeed IS very often used for p-values (with the ever popular t-test) and has a decently strict list of assumptions (which, like those of [O|W|G]LS are very frequently ignored).

[pocketsand]

z-scores just require knowing a standard deviation and a mean. you only need an assumption of normality if you want to do things like assign p-values. of course, that is mostly how they are used.