People who use acid to harm others await a severe punishment in the hereafter.
To think someone attacked a mother and small children! Such depravity. May Allah have mercy on the victims.
Allah (swt) established Qisaas (retribution) for two benefits:
1) A form of justice to the victim.
2) A deterrent for other perpetrators.
If you know that you will be killed if you murder someone, or your eye will be gouged out if you do to others, then these crimes will reduce considerably.
Shari’ah is not man-made guess work as current systems. It is divine law which ultimately benefits all in society.