This would of course depend on a myriad of factors, Time period, ship, climate, captain, conditions and a great many other factors would affect losses among the crew and I think it's a bit unfair to say that shipowners exected a 50% mortality rate on a given voyage would die from scurvy. That wasn't the case. The quote, to the best of my knowledge, comes from Cathrine Price's article The Age of Scurvy in Distillations, a publication by the Science History Institute. She in turn quotes Stephen R Bown, a Canadian historian and writer who, if memory serves, uses a slightly different quote in his book Scurvy: How a Surgeon, a Mariner and a Gentleman Solved the Greatest Medical Mystery of the Age of Sail. He says that this was expected on a "major voyage" but does not, to my recollection, define what that is. That said, I think we can safely assume that most voyages in the age of sail were not major voyages. The term usually applies to famous journeys by explorers or captains whose names we all heard in history 101. Columbus, da Gama, Anson and so on.

No man will be a sailor who has contrivance enough to get himself into a jail; for being in a ship is being in a jail, with the chance of being drowned... a man in a jail has more room, better food, and commonly better company.

-Samuel Johnson (yes, that Samuel Johnson)

So why would a man become a sailor at all? The answer of course if money. Merchant sailors were generally fairly well paid and enjoyed decent food and relatively light work. Added to this, the risks for most sailors on merchantmen in peace time were rather limited. Most journeys were relatively short, there was no risk of getting scurvy because you had fresh food for the duration and in all fairness, much of sailing is really a lot of sitting around. That isn't too bad a prospect. Besides, becoming a sailor may well have been one of few career paths open to some people. I hope this in some way at least explains why some men chose to become seamen. Now, good able seamen are of course highly desireable to another kind of employer, one with somewhat harsher terms of employment. The navy.

Don't talk to me about naval tradition. It's nothing but rum, sodomy, and the lash.

- Winston Churchill maybe.

Now, the navies of continental Europe are altogether different beasts from the merchant sailors. While the pay was, at least periodically, not bad, conditions frequently were. Especially when at war. Even more so in the navies of the global powers who were tasked with defending vast and inaccessible empires around the globe. Long journeys, harsh discipline, occasionally poor supply and cramped conditions is a recipe for scurvy, typhus and a whole host of other nasty diseases that will decimate a crew in short order. Most continental navies did what the armies did, they tried recruiting volunteers and when that didn't raise enough men they conscripted the rest. Being conscripted onto a naval vessel is not a great prospect. Your term of service is whatever length the ship was commissioned for and you might be sent far from home at great risk for a very long time. Needless to say, the navies had a difficult time finding volunteers. Britain faced an even more interesting problem because British citizens were not subject to conscription.

But let's get back for a moment to the original question. Who in their right mind would volunteer for this? The answer was not infrequently, desperate men. The navy offered two months pay in advance to any man who volunteered as well as better pay over all. So if you were hard up for cash, the navy might have been a last resort. Another interesting quirk of British law is that debt collectors were forbidden by law from seeking to collect debts incurred before enlistment. What drives the individual to enlist varies of course, some may have joined from a sense of adventure, others patriotic duty. Others still may well have volunteered for less that voluntary reasons.

The press gang (no, not that press gang)

While Britain did not technically conscript men into naval service, they did something very similar and perhaps more nefarious. The infamous impressment, better known as press ganging. A press gang is basically a more aggressive recruiting crew empowered by the crown to force men into naval service. However, it's not quite as nefarious as sometimes portrayed in fiction where sailors would get drunk with a man and wake up on a ship bound for war. The press gang usually tried to encourage men to volunteers first, of course with the underlying threat that should they not volunteer, being pressed into service would happen anyway. So why not take the sweeter deal of two months pay up front and better monthly pay? Right? I think we can safely assumed that quite a few sailors said "Right" and volunteered when confronted by a press gang. There was only one real downside to that, a volunteer who deserts is hanged, a pressed man who deserts is merely returned to service. And desert they did.

Press gangs operated in costal towns and villages, aboard naval vessels (where they frequently stopped British merchantment bound for home to press a portion of their crew into service) and sometimes even inland or in British colonies. Their activities were usually a source of great discontent, especially in the colonies.

I hope this helps answer your question, at least in part. To summarize, they usually didn't, at least not for the kind of high risk assignments that incurred the kind of losses cited by Bown. The ones who did frequently did so either because the alternative was being pressed into service or conscripted if they didn't or because they were desperate for money/avoiding debt collectors.

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