You can make a better decision if you have the context of the actual thing you are reading, both in terms of how it's presented (the non-textual aspects of a webpage for instance) and the language used. You can get a sense of who the intended audience might be, what their biases might be, how accurate this might be, etc. By using a summarizing tool all that is lost, you give up using your own faculties to understand and judge, and instead you put your trust in a third party which uses its own language, has its own biases, etc.

Of course, as more and more pieces of writing out there become slop, does any of this matter?