Really the only reason why I don´t buy all organic is that the variety is still a bit limited and also I think that higher grades of tea pesticide use should not be such an issue as with lower grade teas. It´s actually quite common for farmers that focus on premium products to use organic farming methods and not seek the certification simply because certification is expensive. They will also have some product certified and sell it at a higher price than non-certified product from another batch grown on the same farm with the same techniques. This applies to both tea and non-tea organic products. Sebastian from Jing Tea Shop has talked a bit about how this applies to tea...and I´ve worked in an organic grocery store where I learned quite a bit about organic certification and where food comes from.
Around Christmas and Thanksgiving they got a LOT of turkeys in stock...some organic and some free range. The organic turkeys were very small and expensive, the free range turkeys quite big and not much more expensive than conventional factory farmed turkeys. The inside scoop is that both the organic and free range were from the exact same farm, they were raised and fed exactly the same way. The organic ones had to be culled earlier so they could be tested before thanksgiving is why they were smaller and the testing raised the price a lot. So non-certified was fresher, larger, and a better price but both were raised in exactly the same conditions.

That´s an extreme example though the extra cost, time and effort involved in getting vegetable products such as tea organic certification is certainly an issue...and it´s why I feel pretty good about buying non-organic tea of high grade from trusted vendors.