Dividends should be paid when the company can no longer reinvest its earnings and expect an outsized return.
By not paying dividends, GILD and its board are signaling that they have plans for the money (R&D or strategic acquisitions) that will provide outsized returns. This is generally a positive sign. Conversely, it can be seen as a negative when a company starts to pay dividends, because it is a signal that the company's internal growth prospects are dwindling.
Dividends aren't good or bad, but they can tell a story about where a company is in its growth cycle.