No, sometimes pay is the original issue.

But if they choose to leave, do not offer them money to stay. Any employee who stays is not being very smart, the only interest the company has in paying you more is keeping you long enough to train your replacement.

If you were not worth X the day before you quit, how are you suddenly worth X the day you decide to quit?

I've seen people accept a counter-offer from a company, and very few of those lasted more than 6 months, or the amount of time it takes the company to make them no longer indispensable.