I see plenty of reasons. Although great at the "suffocating" part and forcing extra shots, he is primarily aggressive, a baseliner, with a fantastic two handed backhand, all the things that are a big plus in my book. Not Fed-level "flashy" for sure, but his groundstrokes are still great to watch, a lot of times to me it seems that he makes it look easy too. Whether he is dominating or having a challenging battle, I find it fascinating watching him solve his opponents. Watching someone who, although doesn't have a GOAT-like forehand of Fedal or a monstrous Pete serve, is such a complete player with many dangerous shots and barely any weaknesses, I always wonder how is he going to get the better of his rival in the next point, or the next match or beyond. And he is a cool guy off the court as well as a nice bonus, not taking himself seriously every second... Djokovic is stunning on many levels, and tennis would have been much poorer in the last 13 years or so without him in the mix.