Kinda makes sense in a way. Usually authors are forbidden from putting the 'final' version of a journal paper on their website* but are more than willing to email you a copy if you ask nicely. I don't see why automating the emailing process should cause any legal problems. Of course, I'm only speculating, there might be other reasons.

*one woman in our department always refuses to correct 'color'/'colour' in publications for american journals so that she has an draft she can put on her website which is almost identical to the final version