You've never played Cav have you...
Not recently. And I'm pretty bad cav. But that's because I was actually charging aware opponents like a fool. Smart and good cav almost never charges alone and aware opponent, even if it is a peasant. Great Khans do but only when there is more than one.
However I've seen you playing yesterday with great lance. You've killed me twice from behind, while I was busy fighting someone. That's how cav kill and couch is much better for that because it delivers more damage than thrust attack and it's harder to miss.
I had pretty low opinion of cavalry then I've decided to try it out and my opinion went up because I wasn't good cav. But after I've played as a peasant with quarter staff, seeing mighty lancers who avoid me even though they can outreach me easily, I must say that my opinion of cavalry now is one big fat zero.