Why do you think fossils are found in sedimentary rocks and not in igneous or metamorphic rocks?

Because igneous rocks are melted rock and metamorphic rocks have been under great pressure and are squashed or stretched and fossils wouldn't be able to survive these conditions.

Fossils are found in this rock because the rocks aren't formed from temperatures that would otherwise destroy them. Igneous rocks are formed by the cooling of lava, and metamorphic rocks are formed by another rock that undergoes extreme heat or pressure. Therefore, they both require heat, while sedimentary rocks are simply formed from deposed sediment from water.