With the yoghurt it wasn't that u couldn't find unflavoured, I did. It was just plain yoghurt, not natural which was skim milk with thickners.
And yes, it's surprising the things that contain sugar. I do like sweet things, but you do need a break now and then.
You should have no problem finding plain yogurt without sugar.
And no problem finding whole milk yogurt without thickeners. But a lot of brands do use thickeners in their low- and non-fat versions.
If you are shopping at a supermarket, you will have to read the labels. If you are mostly eating at restaurants, they will be more limited in the variety of yogurt that they carry.
For those of you wondering about thickeners, a lot of flavored yogurt uses pectic or gelatin or corn starch to give "body" to the yogurt. Even some organic brands use pectin or milk protein concentrate. What is used varied from brand to brand and even within a brand.