I do browse steem posts every now and then, often on my computer and some times on my phone, on my computer I have tools to help me read long posts but on my phone reading is just a pain.
Often a post gets my attention through its thumbnail or the title but when I open the post I face a wall of text and I don't feel starring at my phone for an extended period of time before I realize that it wasn't what I imagined to be.
I need a TL; DR to help me decide if a post deserves my time, attention and vote or not. I guess it's a good habit to add the TL; DR to the end of our posts, it helps mobile users and lazy people without spoiling those who want to read through the post.
Add a short version of your long post for those who want to know what your post is about before reading the whole thing.