To answer your question truthfully, I do not think most mathematicians expect anything from mathematics education as a discipline. It is not even on the radar.

The vast majority of mathematicians have never had any formal training as teachers at all. When they get jobs as educators, there is no kind of systematic support for teaching. There might be services available if you seek them out, but basically the good teachers are all ready good, and the bad teachers generally do not care enough to seek out help.

I have no idea how to change this, or even whether changing this would be a good thing. In my experience the vast majority of mathematics education research is essentially at the level of anecdotes. I think that meaningful education research is only just now starting to be possible, with the kind of huge data sets we can now gather on students taking courses on computers.

If you personally want to improve mathematics education at your university, then probably you should try to make friends with as many mathematicians as possible, and see if you could personally work with them to change their teaching habits. Try to make it fun.