Never realized how difficult writing dialog could be until I literally saw how much space it takes on a page. I have two how-to books on the subject alone. When you realize that screenplays are best written thru direction (action), instead of revealing the plot thru dialog the way a play might be written, then it becomes a obvious how selective a writer must be when putting together sentences.
Somehow IMDB sent a notification of accomplished screenwriters on the subject of dialog.† I sometimes add movies to my watch list (on IMDB) but I don't know yet how this became a tid bit, unless Greta Gerwig was the key. I didn't know she was a screenwriter, but I may have added her to my watch list because of a movie I may have seen worn her in it. Also, I might have added Nicole Holofcener to my watch list because of I like her Catherine Keener films.
† http://blogs.indiewire.com/thompsononhollywood/screenwriters-on-writing-ny-times-asks-linklater-polley-holofcener-delpy-gerwig-and-many-more-about-the-art-of-the-script