Nobody offers a service out of the goodness of their heart.(in 99.9999% of cases)
People would do well to think about services such as randowhale. Now I'm not saying they're crooked or anything like that, what I am saying is all these services are asking for you to pay [something] for the resteem, lucky dip vote etc, you may well earn a couple of dollars out of it but they will be earning far more. Also, as has been pointed out, it encourages people to produce low quality bilge that takes little to no effort to produce with usually a 4 - 1 return ratio by using an upvote service.