So, we figure out from a reverse engineered parser what a given abilities %AP and %WD contributions are? Wait, no, potency already standardizes that...
Our actual damage? ...That's shown on the screen and in our battle logs.
Damage rate? ...Can technically be calculated by hand via timestamps...
Our in-encounter crit rates? ...DoT ticks aside, that's in our battle logs and can be calculated by hand.
PPM? We use true RNG, not RPPM, so this is not estimable outside of the same information we get from our tooltips.
The actual effects of our secondary stats? We already have these spreadsheeted, and would transparency really be so abhorrent? (Also, even this has no reason to be revealed by a parser.)
I can see why SE wouldn't want to open up a slew of api's that third-party addons can then use to check for and report incoming attacks, etc., in what few ways they cannot already (e.g. from /say or /yell cues, though we already have the tech to do that, just no update), but a parser is just not the gateway for any of those.
Take a look at the breakdowns for WoW's own competition with its addons: different devices reveal distinctly different components. All that a parser can reveal, has already been revealed -- not even by third-party parsers, but by the game itself.