Yes, the manager shouldn't take that into account.
The problem is, people work for money and they want that money to live their life as they wish. Be it traveling the world 3 months per year or raising a family and buying a big house. They will tell you why they want a raise and you should understand their reasons: You want employees that perform and an employee that is happy raising their family because they have good work/life balance and the money they need would always perform better than one that just thinks he's not valued or not getting his economic needs covered by your compensation.
As a manager, you have two risks:
1) They leave, which in mid-term could be a blessing or it could just mean bad times for you. Nobody wants managers with high turnover on qualified positions - your team is never performing close to 100% in that case.
2) They stay. Unmotivated, venting their problems at the canteen with their colleagues, who start to think about theirs... You know, the rotten apple. This is most of the times not on purpose to hurt you or the company, it's just a de-stressing mechanism.
Employees are (still) human, so in order to be a good manager you need a holistic view over their needs and worries. After all, you're managing people and not software.