These developers got their start during the Major BBS 6.x, Worldgroup 1, and Worldgroup 2 DOS-based BBS era, when the DOS systems used DLLs. This meant that the ISV could compile the module and distribute it to Sysops - they did not have to provide the source code and the operator did not have to compile his/her BBS. Better for everyone. Business was at its best during this era.