> The question is why corporations think they can be leeches though

Because they can, they don't just think they do. Everything about the framework they operate in allows or even encourages them to do it.

> That's just not right.

As a matter of morality, you're right. This is something very few people or corporations concern themselves with just as soon as there's real money to be made by not concerning themselves with this.

> The question is why corporations think they can be leeches though

because they can be. They do not think they can be leeches, they know they can be leeches.

> That's just not right

I somewhat agree with you, but they do actually have permission to do it.

IMHO, this is the wrong way of looking at it. You can choose any license you like. Choose the right license, and that should be the end of the discussion.