I'd describe it this way:
For those in the target market for whom "runs on Linux" is a positive trait, there is no need to mention that these products are based on Linux: they already know.
For those in the target market for whom "runs on Linux" means nothing, there is no value in mentioning that these products run Linux.
For those in the target market for whom "runs on Linux" is a negative trait, there is an incentive to not mention Linux.
Educating the public about what Linux is and does, and which products use it, is a goal that is largely orthogonal to the objectives of companies that want to make and sell products that use Linux. Users want to complete their tasks; if Linux can do this and the product performs well and is available at a decent price, it will succeed whether people know they are using Linux or not. If it can't, it won't, regardless of whether or not people know it uses Linux.
The value in knowing the identity of a platform comes when it becomes a broad ecosystem, the way "Windows" became shorthand for "runs all the applications you've already invested time and money in"-- those applications you bought and trained people to use in order to accomplish your assigned tasks. To some extent, iOS also has a similar identity, in that tablets running other mobile operating systems may do everything iOS devices do as well, or perhaps even better, but that means less to people who have ever-increasing stables of iOS apps they wish to continue using.
The Linux ecosystem is very deep, but is centered squarely around servers and software development, and less around general productivity, communication, or entertainment-- the things most people use computing devices for. People already use lots of devices that contain Linux all the time-- DSL routers and switches, for instance, but most of them don't know these devices run on Linux, and they don't need to.