WA is a cult game (generally all 2D Worms series). Nowadays I can see that old and well known titles among gamers are being released to download for free - it's
GTA series (I and II) or
Empire Earth and it expands. I don't actually believe that, without advertising campaign and hiring a team to work (which obviously cost a lot), WA will experience another succes (and yet it's doubtful). It's not worth to put effort to bring Worms alive since it'd be a risky operation from Team17 stuff - I mean, the money invested in the revival could simply not reflect with a wide coverage.
Instead, with WA free to download, it makes new prospects for increasing the activity with much lower cost - advertising cost would limit, because the goal isn't anymore to gain profit from the game, you just give people an opportunity to download a cult game for free which isn't supported anymore by Team17 and doesn't make any profit anyway. Why not then? CS and DC are doing great work with WA, it's passion. I truly believe one day they get rewarded for the amazing job they constantly do, for free...
Releasing a non giving any profits title for free by such company as Team17 could unite quite an amount of new/old players you desperately look for. It doesn't mean to make profit from this, except CS and DC case, they obligatory should be lavishly paid.