[gowld]

Shouldn't you be paying full attention instead of taking redundant dictation during lecture?

If you weren't stuck with following a chalkboard, typos could be fixed once and for all time at the source, instead of reappearing at random in every lecture.

[magicalhippo]

But that's the point, I was paying full attention. By writing things down, I had time to process and think about what I wrote. I had time to fully follow the derivations. And that's in addition to the reinforcement effect that the act of writing has (at least for me).

Merely sitting there passively listening would not be paying full attention.

Of course, this required the lecturers to write in a suitable tempo.

[ubercow13]

In a way writing is part of thinking with mathematics. Try solving a long complex homework problem without writing anything.