As i've stated before, i don't have a lot of info about this either.
The 'sudo hdparm -B 254' command actually modifies the power management 'policy' for hard disks.
Setting it to 255 disables power management while 254 is like 'full performances = minimum power management' and, thus, increases the amount of time between two head parkings. (obviously, setting it to 1 does the exact opposite)
For more info about the hdparm command, read the manual page ('man hdparm' in a terminal), or check the gentoo links i gave previously.
I agree that the hdd lifetime concern is a bit worrying, but i guess the developpers have to make a choice at one moment for that stuff to accommodate most of the users out of a standard install process. We seem to have a bit more tricky disks that require fine tune to work properly.
Linux in itself is not to blame on that, it gives us all the tools we need.
Now we only have to fully understand the thing to set the appropriate config...