Why would anyone get rid of a good asset?

[Spencer Keables]

OK this is a question that I have had in the back of my mind for a while, why would anyone sell a property that is cash flowing? 

I realize that some people might want to sell their property to invest in a better property that gives them more of a return. Also I know that there are people that are just bad property managers/owners who might be looking to sell to get rid of a head ache. I can imagine some owners are forced to sale because of financial problems.  Other than the reasons I just mentioned why sell a property that is clearly cash flowing? I can't help but to think that most sellers are ditching their property because they have some underlying issue with it; an issue that will be very costly in the future. Obviously this makes me nervous as an investor. Out of curiosity, for those of you who have purchased/sold a property, what caused the seller or you to part with it?