I am always curious why people do anything they do--good, bad, or indifferent. Sometimes people have motives you would describe as bad. Sometime they have motives you would describe as good and can be kept just as confidential. More often things are very grey and people have a multitude of interrelated reasons for doing the things they do and many of those reasons are very different from what's on the surface.
If your assumption is always that these reasons you don't have immediate access to are negative, you should probably check yourself. If you are only looking for what is negative, you will find it more often. You will sometimes find it when it is not there. You may also question whether you are of authority to deem which motives are or are not pure enough and by whose standards.
If you are to benefit from the curiosity, you must find balance and strive for understanding rather than condemnation.