ttyd0/cuad0 - why is there still this duality ?

[Christoph P. Kukulies]

Just a question. Maybe it isn't true but to me it seems there
is still this duality between ttyd and cuad serial devices.

Why is that? I'm just asking because someone I was talking with 
about modems an comm programs was 'criticising' this fact
in FreeBSD "while other systems long have abandoned this dualism"?

--
Chris Christoph P. U. Kukulies kuku_at_kukulies.org