"Aspirin is simply a manufactured element of willow bark."
Aspirin is a synthesized version of the compound identified in willow bark as the primary active ingredient. It i no way comes from actual willow bark and, like all sythetics, is not the same as the natural version.
I am not sure that millions hate Michelle Obama for her advice on diet and exercise, but I can tell you why so many are unwilling to follow such advice or advice to quit smoking - because maim-stream medicine has spent billions and billions promoting the idea of obtaining a "cure in a bottle", and though patently wrong, it is far easier to take a maim-stream drug - such as aspirin - and continue with bad health habits than it is to make the effort to live and eat healthily.