I think likely as @Hotclutch I mean... Some people doesn't need 120 payment methods in a single e-Commerce shop.
That may be more efficient to gather them 1 by 1 when we have needs for.
Anyway, all of additional payment methods (which was involved to be included in core) would be aswell free as... external plug-in.

The result to have unwanted payment methods can also lead to security breach (even not-installed/not-enabled, due to the fact files will be here aswell) (I mean since modules aren't all useful for payment/shipping stuff, why include them into main OSCommerce 4 release (and furthermore releases)).

Just my thoughts on it, but when I develop an OSCommerce site, I only have the use for 3-4 payments methods.
Perhaps, for a GIIIIIIANT site, ... it will be useful, but not for a small one, but also perhaps I'm wrong.. ?

Anyway, I love what I see in term of ergonomy and features! Keep up that excellent job on OSCommerce future