As someone previously mentioned, modules were more popular as midi accordions became popular. Digital accordions (Roland,SEM,Musictech,Siwa,others) and hybrids with on board sounds became all in one solutions and midi accordion demand (I believe higher in Europe than in US) has fallen off..arranger module production with it.
All in one convenience without additional cabling, stands,and set up time seems to come out on top, especially for live players looking to streamline setups for keyboard and accordion players.
Makes Ketron's latest keyboard offerings looking very good, albeit with the nagging support history of the past (improving now) and limited size and marketing approach..