Why are TED talks 18 minutes long (or less)?
My answer to Why are TED talks 18 minutes long (or less)? on Quora
I imagine it’s because enforcing a shorter talk time results in consistently higher quality presentations, by forcing speakers to carefully structure their talk and strip out any unnecessary details.
A similar logic holds for five minute “lightning talks”, which are extremely popular at technical conferences. Only having 5 minutes forces people to get straight to the point and stay there.