When we use our phones we use letters in a short form instead of the actual word sometimes, example of this is “ttyl”. Ttyl means talk to you later, but the reason we say “ttyl”, instead of the actual word “talk to you later”, is because it is shorter, takes less time, and it is commonly used making it normal it use in our days so far. We as human beings have short patience (sometimes). And since that is the case, when we use the short form of “talk to you later” it makes the conversation shorter making us (the people texting), more interested. But if you took time, typing every word in your sentence without the short form of it (like mentioned above), the person waiting for the response may get bored or lose interest, or look at the message later. However there is downsides to this, someone may be more formal, or older, like an adult or teacher or doctor, etc. And they may not like using this as it is unprofessional. People also can use this in real life, when talking in a convo, face to face. They can say “ttyl” or “talk to you later”, but talk to you later actually is easier to say than “ttyl”, it just doesn’t match the conversation.