Something tells me I don't know the real reasons why tyre treads are made in symmetrical, directional, asymmetrical.
Symmetrical tyres generally are for just peeps who want something 'black and round'.
Generally they are at the very bottom of the 'performance' attribute scales, and generally at the cheaper end of the spectrum. Often fitted to small cars like Matiz, Yaris, Fox, Colt, Fabia, etc - and are generally never lower than an 80 profile (though no doubt someone will find some 60 series symmetrical tyre
).
Directionals, THE main reason why directionals were developed was tyre noise. Most directionals will be able to maintain a continuous contact of
one 'section' of rubber from the centre of the tread to the shoulder. This means that the tyre carcass can be made slightly weaker. However, this then has a distinct disadvantage when the tread depth wears down - the tyres then become very unstable, especially over white lines/cats eyes/overbanding/ironworks, and even truck ruts. Aside the reduction in road noise, directionals generally perform very well in straight lines - so all you drag-strip tarts might like them. Big disadvantages with directionals are the shocking tendancy to aquaplane, especially when tread depths wear to even modest levels. And directionals are NOT particularly good at cornering - despite what any die-hard GSD3 or Yokohama AVS Sport
fan boys addicts may try and claim!
Asymmetrics are simply the the ultimate answer for cornering. They don't suffer from aquaplaning in anywhere near like directionals are prone to. Asymmetrics do generally need a slightly stiffer carcass across the tread area compared to directionals (and those who fail to use a sturdy enough carcass are generally shown up when the tyres have maximum tread > ie Pirelli). Asymmetrics are generally much more consistent throughout their tread wear lifespan, and tyre manufacturers can elect to use two (or more) differing rubber compounds on the same asymmetric tyre (though the current fan-boy choice - the Goodyear F1 Asymm still does NOT use dual compounds).
Unless it's something to do with consumers preferring pretty looking treads.
Sadly, that is a well known issue. I bet 99% of motorists think that if the tread pattern 'looks' good, then it will perform good. This is probably the main reason why peeps still seem to think that directionals can out-perform asymmetrics.
All I know is that I have found the GY F1 rubber to be more confidence inspiring in the asymmetric format than the directional.
Exactly - I think that if you can get rid of any perceived prejudices over directional tread patterns - then asymmetrics (from any tyre manufacturer) will (or should, if they've done their homework properly) always win over their comparitorive <sp?> directional offering.
Do tell, and put me out of my misery. 
Any help?
EDIT: fixed some spelling and incorrect wording.
