There are many reasons to send a real mail instead of an e-mail or SMS. For one, mail is a more personal form of communication. It shows that you took the time to sit down and write a letter or postcard, which can mean a lot to the recipient. Additionally, mail is more permanent than an email or SMS, meaning the recipient can save it and re-read it later if they want. Finally, mail can be more efficient than an e-mail or SMS in certain situations. For example, if you need to send a large amount of information to someone, it would be much easier to do so via mail than via e-mail or SMS.