There are multiple problems that affect reliability of drives. One is vibration, the heads are floating close to the platters too much vibration could disrupt the airflow causing the heads to hit the platters. The airflow also disappears when the drive spins down, so it is very important to move the head away. Another factor is that te spinning platter works like a gyroscope, moving sideways or rotating it in the horizontal plane is pretty much ok. Moving it vertically is a bit worse, but twisting is rough on the bearings. Laptops typically spin their disks down quite often. This is not to save power, as it costs more energy to spin a drive back up and seek to the correct track than just leaving the disk spinning at a constant rotation. So this is to avoid the possibility of head crashes and perhaps even wear to the bearings.

A big factor however is power loss. Laptops only predictably lose power, their battery runs low and the system suspends/hibernates itself before we completely run out. However in a car we have possible power dips and loss due to starting the engine, pulling the player out of the sled, a bad alternator/battery, etc. And when the power cuts out, the platter slows down and and the heads have to be moved off the platter as soon as possible. With the drives I mentioned before, when a write was in progress at this time, it wasn't aborted during the 'emergency head park' and so the bits got written in a sweeping arc across the disk.

Laptop drives are typically better protected for the mechanical wear and tear of mobile devices, but are definitely not designed for sudden power failure. They'll probably be able to handle it to a point, but where that point is exactly...