An example would be where the tailgating driver (the driver in the following vehicle) threatens damage to the leading vehicle and its occupants by driving aggressively — perhaps also with use of headlights and horn — to bully the leading vehicle's driver to get out of the way.
The driver being tailgated might not wish to comply, especially if doing so would involve breaking the law, such as by increasing speed beyond the speed limit or changing lanes without due regard for safety.
Another instance may occur where the leading vehicle is showing directions to the trailing vehicle and the trailing vehicle attempts to avoid allowing an interloping vehicle to come in between them.
Another instance whereby the practice of driving on a road very close to a frontward vehicle or at a close distance may occur is during an occasion whereby the drivers of the two cars are acquainted to one another.
This may be due to it being a procession of motor vehicles, typically carrying or escorting a prominent person that wants to avoid interlopers.
Evidence shows that more experienced drivers are more likely to be involved in rear-end collisions, possibly because they overestimate their skill and become complacent about allowing sufficient distance to avoid an accident.
In its most uncivic form, it can be a case of road rage and/or intimidation.
Note, however, that in some jurisdictions flashing high beams is a normal and polite method used to signal the intention to overtake.