why, you might ask? because it saves all of your texts with one person as a conversation and you can go back and read them from months earlier, as long as you don't delete them.
i just randomly decided to delete my huge log of text conversations and came across the texts between my mom and I, since May 10, when I got my iPhone for my birthday. As I read them all, I miss her so much and wish I could text her and get her often, silly response, of "hehe snort snort, i love you today". (no joke she really wrote that).
the last text she ever sent me said: "Have a wonderful day. casting all your cares upon him: for the careth for you. 1 Peter 5:7. Love u, honey." That was on July 8th at 6:36am. She texted me almost daily, in the mornings before work, to tell me she was praying for me or to send me little encouraging notes like this one.