It's a cart and horse problem, nobody wants to use it because they think there's no investment, since developing it could be seen outside as being an indemnification of the person.
Lack of use means that less people even want to invest in developing it further, making it take a back seat, which then leads to even fewer scenarios where it's used, because it's not competitive, and so on.
The Linux kernel rarely removes stuff. This is not something that should be taken as a measure of support; If we want to track reiserFS properly we must follow the commits before prosecution and after, along with some usage trends would paint a real picture.
There's a whole host of dead things in Linux (AFS, which even Apple doesn't support for nearly 2 decades) that isn't removed yet.