IMO, ABSOLUTELY. Warm up ANY engine before putting a load on it. Car, bike, airplane, lawnmower, whatever. It's important on any engine, but critical on aluminum engines. Cold aluminum is weak, it wears and breaks much easier when cold. It needs to be warmed up slowly, with as little stress as possible on it. Aluminum expands quite a bit as it warms up, and warming it up too quickly (like putting a load on it) can cause thermal cracking. There is also the matter of clearances. Engines are designed to have correct internal clearances at operating temperature. The clearances will be incorrect when cold. Many people say you should take off immediately, but ride very slowly for a while. This can work, especially if the ambient temperature is fairly high. I have done it in cars, by driving around the neighborhood at 10 mph for half a mile or so. But not on a bike. When I put that bike in gear and take off, I want it warm enough to be able to whack the throttle wide open if necessary. It is also more critical to warm an air cooled engine up slowly, because they tend to warm up faster than liquid cooled engines, and have a greater difference in clearances than liquid cooled engines. It doesn't take long to warm up an air cooled engine in normal temperatures. Let it idle for 5 minutes and it is pretty much warmed up. My Sportster has an oil temp gauge, and I let it idle till it reaches 100 degrees before taking off. Also, on a carbureted engine, turn the choke off just as soon as it will run without it. You want the leanest mixture possible during warmup, because a rich mixture can wash the oil off the cylinder walls.
Modern engines typically have such a long lifespan that people don't notice the damage they are doing by not warming up the engine before taking off. John Muir, an engineer who wrote the Volkswagen Idiot Book, claimed that not warming up an engine before taking off would reduce it's life by about 30%. Most people never put enough miles on motorcycle engines for that to ever show up, so they never see the results of not warming up their engine. The same thing can apply to not changing their oil often enough. They get rid of the vehicle before the damage shows up, leaving the next owner to deal with it.
For those who wear a lot of gear, just start the bike, then put on all your gear, and by the bike should be ready to go.