Ancestry don't make any pretence to be anything other than a commercial organisation. They don't obtain and index their information at zero cost, and they aren't staffed by volunteers.
If they allow a free sample of one of their products for a while in the hope that the people who make use of it then take out a subscription - what is so surprising about that? My local supermarket sometimes hands out free samples, but I don't think anyone helps themselves and then complains that the grasping store owners are only trying to make money out of people's natural liking for a glass of wine.
Even though their products are flawed, a subscription to Ancestry is an awful lot cheaper for me than traveling to all the places where the originals are held, and good value as far as I am concerned.