The reverse threaded lock ring keeps your cog from un-threading itself when you apply back pressure to the rear wheel... this can be catastrophic as once loosened the cog can unscrew itself while you are riding.

Many people use suicide hubs where a cog is threaded on with loctite and a right handed bottom bracket ring is added (also with loctite) and with a brake and proper assembly, this can be a very solid setup. I have ridden 10,000 km on such a hub and there is no way that cog is coming off without a torch.