Solids

Are solids for babies necessary? My 7 month old only drinks breast milk and doesn't eat any baby food. She is really picky and won't eat it. Tried different baby food brands, tried every flavor, even baby yogurt. I've also tried making it fun to encourage her and even pretend eat it too. She doesn't like the oatmeal or rice cereal. Do the need solid food, or is it really just for new tastes and textures?