Lets start with a small explanation about engineering and science. There is engineering and there is engineering science. Engineering science is like normal science only focused on engineering thing. For example, at the moment there is a lot of research in the structure of the internet. This research can be used by others to make recommendations and to create systems based on that idea, just like with research in every other scientific discipline.

Engineering uses science in order to create something. Various things can be created, like cars, computers etc. But not all these things are for the public to know, like how to build a atomic bomb or how to genetically engineer a super influenza virus. These are good things to actually research, but you'll want to keep access to this kind of information restricted.

Another point to note is that engineering mainly takes place in companies. Companies don't want everybody to know how their products work, while the things they used may be very interesting research topics. This also means that there was no public funding, so the company can do with the info what they want.

I know that a pay wall is probably not the best solution, but engineering knowledge is not always good knowledge to give to just anybody.

EDIT: added a small bit.