He’s the host of the show, so his status might be higher than the chefs, so that might be one reason why he drops it. A higher-up might drop the “san” when addressing underlings.
More likely, it’s because the chefs are celebrities. When I hear the names of celebrities being said on TV, I don’t ever remember hearing a “san” used after the name. Not out of impoliteness, but because these are Big Names, almost like brands.
I mentioned a couple of examples above. Also, there are variations on “san.” There is “kun,” used to refer to boys and younger males. For example, at my workplace, there is a 22 year old male. He is referred to as “Takamura-kun.” Using “san” for him would be weird. There is also “chan” for young girls, but generally, you stop calling them “chan” when they get around adolescent age, although they might refer to friends as “A-chan.” Close friends might drop it altogether when talking to each other, and of course, you don’t use it with family members.
By the way, you can use the “san” with a full name, e.g. Yamamoto Kaori-san, or first name only (see below).
Yes, sometimes it’s used in print. In the recent case of the 11 year old girl slashing her 12 year old classmate to death with a box cutter, the victim was referred to as both “Mitarai Satomi-san” and “Satomi-san” (first name only).
Sometimes, “-shi” is used also. I see this a lot in business correspondence, but it also appears in the newspaper. “-shi” is used for adults only, I believe.
Yes, younger people still use it. I’ve never heard it dropped as an insult. Usually, various rude variations on the 2nd person pronoun is used, or just insult words (“Baka!”).
I can’t remember what they call Osama bin Laden. I think they just use the “bin Ladin” part. GW Bush is referred to as “Busshu Daitouryou” (President Bush) or “Busshu-san,” or sometimes just plain “Busshu.” Michael Moore, in print, is plain “Muua,” “Muua-kantoku” (Director Moore), or “Muua-shi.”
Like I said, famous people, and oftentimes regular foreigners, get the “yobi-sute” treatment, “yobi-sute” meaning the “san” or other forms of address get dropped.