hikermor summed it up pretty well, but here's my take:

The only time you need a petroleum based liquid fueled stove is when it's really cold. There are gas stoves that will work below 0F/-18C (particularly if you do things to warm the canister), but in general 0F/-18C is sort of my dividing line between appropriate use of a winter capable gas stove vs. a liquid fueled stove.

Other reasons to use a liquid fueled stove:

• Motor touring. Liquid fuel is pretty popular with long distance motorcyclists for example. They can just pull a little unleaded out of their tanks and run their stove.
• International travel. Kerosene is the international stove fuel and is pretty available world wide. Av gas and unleaded automotive gas are also available in many areas where threaded backpacking canisters are not.
• "Sustainability." Canisters take a lot to manufacture and are single use. Even if you recycle them, there's still a much greater impact than buying liquid fuel bottle that will last a lifetime (or more)
• KISS (keep it simple, sweetheart). If don't want to have "gear proliferation" and want one stove for all four seasons, liquid fuel is the way to go.
• High volume use. Liquid fuel is still the cheapest fuel. For people that use their stoves a lot, it's a good option. A four ounce canister of gas costs about $5.00. The equivalent amount of white gasoline? About $0.30.
• Nostalgia. Seriously! I've still got my uncle's 1962 Primus 71 stove. It's all brass, and it's highly cool. I'm not going to stop using that or my ultra-cool Svea 123 just because gas is a bit more convenient! Get real!

HJ