Could it simply be a case of the MSX scene being much bigger?
Not only that. Amiga scene has splitted into small groups. Bang HW directly or use OS calls? OCS or AGA or CGX? Paula or AHI? 3D or not 3D and if so, which 3D API? OS1, OS2, OS3, OS4, MorphOS, AROS? The target HW can be anything from Amiga 500 to WinUAE...