They spy because they can. They spy because the companies involved believe that the data they collect has value. They spy because the companies involved believe that the data they collect might have even more value in the future.

The companies involved aren't in the business of selling you stuff. They sell data about you to others. Sure that might be a retailer of Hello Kitty backpacks with scenes of unicorns shitting rainbows. It might be a presidential campaign. It might be a government - and in that case, the value exchanged might be trade privileges rather than cash.

Large commercial ventures willing to harm many people for the sake of profit are not unknown to history e.g. the East India Company and International Association of the Congo. Likewise, industries adopting standard practices which do so - e.g. tetra-ethyl lead.

I may be wrong. But I don't think that just because I live in the US corporations have any more respect for my human dignity than they do for the citizens of Honduras or Pakistan or Albania.