Someone pointed out that young people tend to want to show that they are young and modern. By definition, a grandmother is the opposite of young, and therefore anything Grandma does is deemed out of style.

I suppose the commercials aimed at adults want the adults to get the message, "Use this product to show that you have matured past teenage angst, are now more experienced, and have learned a thing or two about life." (Although, to hear my mother talk, I'm still a wet-behind-the-ears upstart who needs the benefit of HER experience.) True that it goes both ways. I don't like to see all teenagers lumped together either--where they are all rebellious, all on drugs, all foolishly impulsive, all lazy, all this or all that. But maybe I was more sensitive to that when I was a teenager, and now that I am a grandmother, the "eww, my grandma does that" is what stands out.