That's pretty common in the ecommerce world. If you just have a single website, then when someone does a search they have to pick your one website out of the hundreds of search results for you to get their business. If you have 10 different websites/brands, then out of 100 search results you now have a 10x better chance that a person will click on one of your sites rather than a competitor. I have a friend who does very well with hotel booking sites (he makes several million a year), and he literally has THOUSANDS of domain names - phoenixhotels.com, visitdallas.com, cheapcaribbean.com, etc - which all use the same backend booking software, same support staff, same parent company, just different different virtual storefronts. And a lot of times it just happens as a result of an acquisition, like raggmann54 mentioned GG bought 3Balls but they kept both sites/brands going.