I agree with NCC320 for my circumstances. On my very narrow beamed boat jacklines seem pretty worthless. When I go forward I need one hand just to keep the teather from snagging. I'd rather have two hands available for holding on. In addition, there is no way I would be able to get back on the boat if I were dumped over on the end of a teather. (I have tried.) If I absolutely had to die, I would rather have some time to bargin with God, say goodbye to the world, and finally and hopefully accept my fate with a semblance of dignity and peace---wishful thinking?---then to be drowned by my boat and become trolling bait.
In a blow I stay in the cockpit or down below. Once the genoa has blown out because I was to scared to go forward. (I've since tried to rig the boat to forestall that.) Besides the headsail I can't think of other reasons why one would need to go past the mast in high winds and waves. Maybe the anchor coming lose on the bow roller and banging up the boat? Anything else?