I've known a lot of great drummers who did zero warm-up before playing some blistering sets. THEY'RE the ones that I don't understand.
I think it's such an individualized preference, based on the music being played, the particular style of the drummer, the psyche of the performer (some dudes are just relaxed all the time), and - most important, I think - the physiology of the drummer.
Some people have more muscle mass than others. Some have denser muscle mass than others. Some people are rich in slow-twitch fibers, other fast-twitch. Some have longer muscles, others shorter...etc. etc.
It's impossible to say whether or not warming up is necessary for any given player; they need to figure it out themselves. As a rather high-strung guy with a respectable amount of muscle mass, I always try to warm up before a gig; once my muscles are properly primed (and a little of that nervous energy expended), I can really launch into a set without experiencing tightness or fatigue after a few songs. I feel much looser, which we all know leads to much better playing.
Sometimes it's impossible to get a decent warm-up. In those instances, I try to just stay loose and pull back just a bit until I break a sweat (usually not too long) - use the first few songs AS my warm-up, in a sense.
One more thing: if anyone can't seem to get a warm-up in before their set - if there's no quiet spot, nowhere to drop a drum pad, seemingly no place to fire off some quick rudiments - I recommend using my patented ThighBlaster® method: grab a hand towel, twist it, and tie it around your leg just above the knee. Now all you need is a chair, barstool, windowsill, or edge of a sofa; sit down and start working on that towel. The lack of response really works your 'drum muscles' and helps fire them up quicker—and again, all you need is a small towel and a place to sit.