I've just read about L. E. J. Brouwer, and his understanding of math as a cognitive construct, communication of ideas between mathematicians. It's important to keep math "user friendly", and not just "print out" results and proofs. Of course, some lectures may be "duller", than others, but it's intuitions, which are to be communicated.

Proofs can be sparingly left as an exercise, where it is necessary to hone skills.

Personally I did not have difficulties following math lectures, when I was studying at the university (I have degree in mathematics). And there were lecturers using quite different styles. From pedantic to those using blackboard artistically. But I can imagine math lectures can be more effective. In any field.