Yeah, it was a nickel and dime move to force you to buy the extension cables... At least, that's what I felt.
Every console I had prior to winning a TurboGrafx-16 had at least 6 feet of length for controllers. From NES to a Genesis I borrowed from a friend, and on to SNES, etc... Atari was OK too.
TG-16 was the only one I opened to find controllers 3 feet in length... And the brochure material showed you the extension cables for $9.99 as I recall.
I always thought that was a crummy move, but is what it is.
Funny you brought this up, I had to learn good solder work and took cable from an old controller to extend my NEC Avenue pad after upgrading to a Turbo Duo. I refused to buy extension cables on principle, cheap bastard that I am!