When it comes to putting older stuff into CC, they have very little motivation. Many of the people that are upset because it's not there will likely just be upset about something else. I can't think of any nefarious reason they'd hold back the 3.x stuff and I have no idea how much getting TSR era stuff ready would take but I don't think it would be insignificant.
So the benefit is close to zero and the potential risk is higher than zero. It's simple corporate math, they don't want to spend money in the form of people's time to review for minimal benefit. Old grognards are the only ones who likely care at this point and they aren't the target audience for significant growth or income anyway.
So measurable cost for hypothetical profit being close to zero equals delay until people need a filler project here and there.