You're correct about Viking, also expedition cruise lines offer extensive enrichment programs, but they are even more expensive. I'm afraid that when you turn to the less expensive mainstream lines, it's a bit of a crapshoot. Most have some form of scheduled lectures, but the topics and quality vary greatly and really can't be predicted in advance. You won't know until you get onboard who the lecturers are and what their topics will be. Sometimes the presentations are nothing more than thinly disguised sales pitches for excursions or the onboard shops. Sometimes they are very interesting. The thing is, you can't tell in advance which you're getting.