Why do companies attempt to prevent piracy if it doesn't hurt sales?

Because companies are reactionary structures of power, they often act out of fear of losing control, not out of data or reason. It's easier to lobby governments for harsher copyright laws instead of modernising business model.

There are many counter-examples.

Gabe Newell (Valve co-founder) famously said:

"Piracy is almost always a service problem and not a pricing problem."

Jeff Bewkes (CEO of Time Warner) famous quote about piracy:

"Game of Thrones being the most pirated show in the world? That's better than an Emmy."

Radiohead released their In Rainbows album as "pay what you want", directly online. It generated more revenue than their previous label-backed album.

It's hard to convince people of X, if their earnings depend on them not agreeing.

Management and lawyers are paid to be busy and "defend rights", not on sitting still and saying that nothing should be done. Even if it true, they still need look busy and "earn their check", otherwise their numbers/salaries can be reduced.

The opinions of their principals may not align with published findings, for many reasons.

Because those studies aren't actual proof, and companies selling things are biased to believe that people won't pay for shit if they don't have to. (Which they won't.)