Here are a few more reasons:
Back in 1989, we bought a Civic. It had:
1) less road grip than Corolla. Far less as a matter of fact!
2) lower pick (acceleration) than Corolla. The poor 1193 cc engine was no match to the more power 1299 (or 1298) cc Corolla. My car lost a race to a Suzuki Alto at the time (the current Mehran).
3) much less comfort than the Corolla. The poorly designed double wishbone Honda suspension left your back and butt hurting after giving you a jump-n-jack jumpy-bubbly ride on rough roads. It was a no match to the more comfortable Corolla.
4) less durable than a Corolla. Soon after I put around 2000km on it (we bought it brand new), I could hear all kinds of plastic vibrations from the dashboards, doors, seat belt anchors, and eVERYTHING else. And yes, the car was built in Japan at the time.
If there was anything better on the Civic's side, it was the body styling, which again is a very subjective thing to say.
So why should people buy a Civic? Granted that Civic has recently improved upon all of these areas, people mind has stuck with the better Corolla.
BTW, besides all that, my family owns nothing but Civics! No Corollas!