Couple of reasons.
1. Those that do know them think of them as home keyboards for home hobby players as this is how they are advertised, and what they were primarily designed for.
2. All the public see is someone either sitting or standing at a box pressing buttons and keys, and to them it is just a slightly more advanced version of Karaoke, however if you use 2 keyboards (On a stand or by the side) and use them both, it looks professional even though you are using them the same as just a single keyboard. (Looks and choreography is everything to the GP these days)
3. Don't worry about it (the number of professional arranger players is minuscule anyway) as your the one that is making the money.

Bill