Good night and have sweet dreams. In case you're really curious, people use 'luv' because it sounds cute to them, or they got used to cutting corners when writing, or they have a fear of using the word 'love' as it sounds too serious/burdening, or they want to portray an accent, or they use it as terms of endearment, etc. Yep, I answered too seriou...... reply
I use luv when I'm arguing and i'm not really as into the argument as the other person and love when I'm being genuine
Like "you look beautiful, love" and the former "I think you should worry about yourself, luv" reply