I think you also have to look at what is the popularity of the anime series outside of Japan.
Especially in North America, there has been a big decline in the amount of series being dubbed/shown on TV. Grant it, not all of the dubbed series on TV in the past kept the original OP/ED, but some did, and it accessed a larger audience. Also, it seems that only the most popular series are even being brought to DVD here.
And like others, I do not watch too many anime series, but prefer the manga versions.
I only have
one song fanlisting, and it has a lot of members, but it was adopted, and the original owner started it back in... /checks ...2004. But the join rate is pretty low. I used to have one or maybe two others in the past, but they were never high membership fanlistings.