Forgive my ignorance, but if these investors are looking for money from a stock that hasn't offered a dividend in 17 years, can't they just sell?
Apple is worth 350 billion. 80 billion of that is cash.
That means Apple's value is "only" 270 billion.
So even if Apple doubles its worth to (2 * 270) + 80 = 620 billion, the stock grows only by 77% (because the cash is mostly just sitting there and definitely not growing as fast as Apple).
The point is this: the cash pretty much belongs to the shareholders. But they don't control it and much of it is just sitting there. A dividend means they can use that money to buy more Apple stock, meaning faster growth.
A stock buyback has the same effect, by the way.