Because they don't know anything anywhere, right? Do you think that the Irish voters know the weighted inclusive Gregory method? Do you think they can explain how STV allocates its representation? No, they can't. Neither can our voters explain to you how 39% of the vote turned into 60% of the seats. Just go out in the street and ask them. They're not going to be able to tell you. That's the simple system. We know they mistake actual legislative majority governments for other majority governments. The public's knowledge is low, and that's because they're busy. Your job is to be the experts and call in the experts as you need them.
The important thing is that the Irish, as an example, know how to use their system. How do we know that? Ballot spoilage in Ireland is actually lower than in our system. We could intuit that if they didn't understand the system or if it was too complicated, as the critics allege, then we would expect to see lots of spoiled ballots, but we don't. Therefore, they understand how the system works and they understand what to use it for, and that is the important thing. You're wasting people's time if you go into all the details, because they glaze over. You have to connect with them on why this issue matters. That's the broader question behind how a democracy should function.
I say majority rule and effective representation. Those are two pretty key values that I think any democratic theorist would get behind.