Random question which probably has an obvious answer that I’m somehow not realizing…

What is the purpose/utility for Air Canada to codeshare a flight operated by, for example, LH?

I get that code-sharing allows Air Canada to sell tickets on routes they don’t fly and couldn’t otherwise market, but this isn’t the case for alliance partners, right?

I’ve noticed recently when booking some TATL flights that the Air Canada website gives the option of booking LH 471 or AC 9104 (its codeshare). Same price.

Is there a reason that Air Canada markets AC9104 when they could just sell seats on LH471, as they already do? Is there any advantage as a passenger to being booked on the native flight # vs the AC codeshare? As I understand it, LH metal means the experience will be dictated by LH regardless, and the 014 ticket stock means I’ll get SQD regardless.