The afforementioned "culture flips" are my #1 reason for razing. I started off playing a typical Civ II world domination game, but far too often when I capture enemy
core cities they flip despite
A) an ovewhelming cultural advantage;
B) an overwhelming garrison;
C) 1000 gold worth of rushed happiness/culture/corruption improvements.
The model is badly flawed, and makes an expansionist strategy much less fun. So I changed my style of play from Roman to Mongol!
Oh, my #2 reason is corruption. If I'm getting close to the "catastrophic corruption limit" for the map size, I can't afford to have more cities (unless, of course, it's
a lot more cities!)
#3 reason is not wanting to have to defend the city/surpress the resistors, either because I'm busy blitzing or because the city is in peril. A bunch of captured workers is lots better than nothing!
Reasons to
keep a captured city:
#1: Strategic resource (to obtain it or deny it)
#2: Pilfer a wonder. I'd hate to burn down Sun Tzu or the Pyramids. But why don't I get culture from my capured Wonders?
#3: Empire growth. This is #1 in the early game, but much less important later, when your empire is already big enough.
#4: Culture bubble. In enemy territory, it can be very important to control a stretch of roads/rails so that your troops can move through quickly
and the enemy are slowed.