You ever watch someone on social media do an "unboxing" of all the PR packages they received that week? Guess what that all is to them? Income. Yep - the Fair Market Value of all the products received should be included as income when they file taxes.
"But that's just a gift they shouldn't have to claim income on that!" But it's not a gift - the courts have rules that something is only considered a gift when it's given with "detached and disinterested generosity." Company's send gifts to influencers in hopes they will talk about the products to their followers. I know I don't have random golf clubs and clothes show up in my mail from these companies because I don't have any marketing value to them.
Ultimately this is a cheap-marketing ploy by these giant corporations to buy-off influencers at bargain-prices. It's much most cost-effective for a make-up company to send an influencer golf balls that cost $5 to manufacture in hopes they discuss it on their channel, than it is to pay them $1,000 to do a sponsored post.

