How can this damage occur?
Physical damage to a mechanical drive can be caused by normal wear and tear. Like most mechanical devices, the parts become worn and will almost always fail at some point. For all storage media however, the bending, breaking, dropping, liquid exposure, bumping, or power surges can contribute to physical damage of a storage media device.
Firmware Damage can be caused by an array of issues including platter damage, failing heads, module damage, SMART failure or damage, SED lockouts, or ROM / RAM failure. The majority of these are not caused by normal user interaction, but are frequent due to the complexity of the manufactures software (firmware). Manufactures try their best to make a long lasting drive, but with so many checks and balances there tend to be some issues that occur.
Partition / Volume Failure can occur from software, firmware, and physical damage. If the ability to read the MFTs, Catalog files, or translator occur, loss to user data (your data) will occur. These can be caused by weak heads, platter damage, module damage, translator failures, etc.