It's simple, Nedim. Look at the ROM styles in any arranger... THAT is what the majority of its' users want, or they would buy another arranger that DID provide what they need. In the Far East, the manufacturers provide specialized Oriental models. In the Middle East, Korg do a grand job at providing styles and sounds for that market. But look at the rest of the world...

The G70 I use has the same ROM styles in it that they sell in London, Paris, Berlin, Oslo, Stockholm, Moscow, Sydney, Rio de Janeiro, Mexico City... Those styles are the 'common denominator' that players all over the world NEED in an arranger. Of course, in addition, they would like stuff for their OWN local market... My playlist needs styles that are little represented by ROM selections as much as anyone else. How many authentic New Orleans beats come with most arrangers? How much Zydeco? How much authentic US Alternative?

We all need styles in addition to the ROM, but those ROM categories have been market researched up the wazoo THOSE styles are not 'niche' no matter WHERE you come from...