AMD probably doesn't advertise because it's a total waste of money. 99% of the users out there don't know the first thing about processors, let alone the fairly complex architecture that makes them work.
That's AMDs problem. What have they got going for them? Well, their processors are better. But the average joe doesn't know that. So, AMD really has nothing in the large scale consumer market.
Intel has Dell. They have years of marketing. They are to processors what McDonalds is to fast food. (only I have to admit, intel has a LONG way to fall before it's as bad as McDonalds)
Fact is, people buy what they know. They know Pentium, so they buy pentium. Breaking into the market is not as simple as making a faster better chip. It means having more attractive, appealing advertising on a gargantuan scale. I am not sure of the exact figures, but I am pretty sure Intel spends more on advertising than AMDs entire budget. So, if AMD channeled ALL of their money into advertising, PLUS got loans in the hundreds of millions for even MORE advertising. AND they kept it up for about 5 years, they would probably see a payoff. Perhaps right before they went bankrupt.
This is why AMD doesn't advertise. It's not cost effective right now.
What AMD needs to do is exactly what it IS doing. Which is gain a good reputation with the hardware sites like TOMs, and with power users like most of us. Once they have that market solidified, they can begin moving into corporate markets, which are more likely to accept preformance specs over catchy jingles. Also remember that in the corporate world, Intel still has a slight edge in the spec sheets. Once they get through the corporate door, they will have the financial base to dump hundreds of millions of dollars into advertising like Intel does.
Bottom line is, Intel is still the undisputed champion of marketing. Their marketing engine is to AMDs what the Athlon 1.2gig is to the P90. In this area they are untouchable right now. So the question is not why AMD doesn't advertise, but why would they waste their money on advertising.