My mother was a functioning alcoholic. She started to develop Parkinson's-like symptoms that weren't Parkinson's because they didn't respond to the medications, but she was never truthful with the doctors about her alcohol consumption and I'm pretty sure it was a factor in the symptoms - like hand tremor and difficulty speaking - and also in the brain haemorrhage that killed her. Though I'm now also aware that some of the symptoms could have been the result of various SBD-invoked deficiencies like Vit B12, Vit D etc, as I think they've contributed to my father's condition.
It's not something I generally follow, but when there's a match on and I have the inclination or motivation (want to see how Murray does because he's a Brit and Djokovic because of his gluten-free/paleo diet) I enjoy it. It's in the details, a bit like cricket and NFL. You have to sit down and watch the whole thing, but if you concentrate on every stroke and where it's landing, then you get to see the progression of a rally where, though a player might return a ball, he's then out of position and the other player has the opportunity to win the point - but only if he gets the ball in exactly the right place. Just like cricket is about each ball bowled, but only really in the context of the balls that have gone before and the match as a whole. Tennis is more reactive, but there's still tactics and strategy involved.