There are numerous arguments claiming this requirement is unjust and that the defendant should be held responsible for the actual consequences of any careless conduct that results in injury, whether foreseeable or not. However, this broadens the scope of the tort considerably and would open up an endlessness of liability.
Further, foreseeability ensures fairness for the defendant. Is would be unjust to hold a defendant liable for conduct which they could not have anticipated would result in injury. Being penalized for conduct which does not foreseeably cause injury would result in numerous frivolous claims. Accidents occur all of the time. While it would be fantastic for the injured party to always have recourse for legal action, it would not be fair to those defendants of whom are undeserving.
There are some injuries no one could predict and no one but the forces of fate should be held responsible and certainly no one should be penalized. This may be unfortunate for the injured party, but the blame cannot always be laid at someone else's feet. Foreseeability ensures blame can only be laid at the feet of those who should have reasonably foreseen the consequences of their actions. This is fair. This is just. Taking away the requirement of forseeability would make the opposite true.