The reason why mercenaries are hired is to fight. A Mercenary is a hired professional who has been trained to fight for a state or nation without any political interest except for money. Mercenaries usually work for private military contractors (PMC); these companies recruit people who have military training and also those who have experience with weapons.
The bush administration ramped up the use of private military contractors during the Iraq invasion in 2003. In recent times, it is also heard that mercenary operative is also involved in Syria, Libya, Yemen, and Ukraine conflict.
There is a lot of risks involved when one is a mercenary, but people still go for it because of the large compensation attached to it when they are victorious. Lastly, mercenaries are not recognized as legal combatants, and they are not protected by any law as captured service personnel of the regular army.