Competition breeds innovation. Just look at cell phones, cellular service, computers, cars, TVs, etc.
Kline, Williams, Atlas, Weaver, 3rd rail, MTH, and others have all impacted the industry. Better detail, graphics, variety, and hopefully quality. Without the re-issues of pre and postwar stuff we would still be stuck in the escalating prices of postwar trains.
It's nice to have more options for sure.