Here's some quotes from children in Bolivia about letter writing (Taken from the Compassion Blog) which sums up how important they are.
To hear direct from the children says it all..
“My sponsor is Nancy. She writes to me often, she sends me stickers and letters, and I feel very happy when she writes to me. She tells me that she loves me as a son and I tell her that she is like my second family.” — David
“My sponsor is Cristina and she writes to me often. I feel happy because my sponsor writes to me. Some children don’t even have a sponsor and I feel happy to have one. I thank God for that. When I write to Cristina I tell her about school, church, my family, the development center and about my friends.” — Reina
“My sponsor is Elmer. He is from the U.S. and he writes to me often. He asks me how I am, how I am doing at school and when it’s my birthday he asks me about that. I like it when Elmer writes to me and I love to write to him. I tell him that I am doing well at school, what I did for my birthday and about when I lost a tooth. But I have many mates that never receive letters and they feel sad.” — Lorena
“My sponsors write to me often. I feel happy to receive letters and I like to write to them. I ask them how they are; I tell them that I am fine here.” — Josue
“My sponsors write to me only occasionally. Sometimes I feel bad because I see how my mates receive letters. However there are some children that never receive letters and they also feel bad. I like to write my sponsors and tell them how I am regarding my health, about my school and the things I did, how my family is, or about the activities I do at the development center.” — Leidy