Making money is one measure of profitability, another is reducing risk, something businesses aren't good at measuring. If there's two star systems instead of one colonized and the risk of one star system being wiped out by catastrophe is 1 in 1 million, then the risk of 2 being wiped out is only 1 in a quadrillion. A similar logic is behind why some people want to colonize the Moon or Mars. And when something has been successfully executed once, it's a lot easier for it to be done again, whether it's colonizing the rest of the planets in the solar system or the rest of the stars in the Orion spur.