There are a few good restaurants that we enjoy, like Cafe Tu Tu Tango, and Bahama Breeze. And there's always miniature golf when you're not headed to the theme parks. The northern end, though, has more than it's share of junkstores and fast food.
To address your question: "Why is it so good to be in close proximity to it?"
We stay at Sheraton Vistana Villages. So, for us, it's good for being close to WDW, close to groceries at Publix, close to some decent restaurants. It also gives us easy access to Aquatica and Sea World, and it's not too far from Universal. The south end of I-drive is mostly attractive resorts. so it's a pleasant drive through there.
We've stayed on site at WDW twice, and if I intended to spend my entire trip at the theme parks, I would recommend that. But, after a number of trips to Orlando, we usually only spend a couple days at the theme parks, and the rest seeing what else Orlando has to offer. And that's the other thing I-drive provides - easy access to the Interstate for touring around.