A lot of times you would like to keep your sights on the relative work. You don't want to miss a key. You have to watch for traffic, so you won't collide with anyone. In essence, your eyes have to pay attention to a lot more than just the altitude. It should make sense then to use an audible altimeter, as a backup to your visual cues.
Some jumpers even use an audible altimeter as a primary altitude indicator.
That is, if you pay attention to the sound and take prompt and appropriate actions. Turn and track when you hear the beeping, not a few seconds after it stops. A different view, proposed by Tom Barnett, about audible altimeters suggests setting them for 1500 feet. Two of every three skydiving fatalities are caused by jumpers failing to initiate emergency procedures at a sufficiently high altitude. The numbers in Table 1 show that 98 of 148 skydiving fatalities from 1982 to 1986 were due to malfunctions or no pull low pulls.