It's always best for server admins to use the 'Enforce Bans' flag within their AccCP on each server. Really the downloadable ban lists are something which should be occasionally downloaded for use in the rare event of the hub ever going down - ensures old bans aren't enforced, etc, etc.
We have discussed the removal of public banlists or the dating of them to only have bans 30 days+ within, not only to encourage streaming but also to avoid incidents where outdated banlists are being enforced. Nothing's changed there for the moment and I don't believe there are immediate plans to either.
If you like public ban lists does sort of encourage streaming because it shows part of what we have to offer, however, promotion is also an aspect to be seriously considered so people know what the benefits of streaming with PBBans are: live banning, MCi configs, etc, etc
In addition to that the banlists are handy for those to use who don't meet our streaming requirements but are able to, and well if cheaters want to enforce our bans on their servers too then they're more than welcome to.
The biggest thing that'll bring in more streamers to PBBans is effective anti-cheat within the gaming community, good communication and promotion while banlists and their availability is a factor... it's part of a huge picture.