Ads are not about being aware of all available choices. It is about presenting one specific choice in the best possible way : not the best way to make an informed decision
The problem is that there's no filter. This guy[1] Thinks we probably see 300 adverts a day, at the low end. Seems about right to me, lets go with that.
If I invest two minutes of research into each ad, I get 10 hours of research, every day. Obviously, it's not practical for me to actually research ads.
Thus, to deal with the raging torrent of imagery being ejaculated at my face by advertising companies, I must fall back to some kind of heuristic. I have two immediate choices: I can assume ads are truthful, or I can assume they are lying.
I know /some/ ads are lying, because I see obvious bullshit like acai berry ads on a semi-regular basis. So if I'm not willing to invest 10 hours a day of research, it's best /for me/ to just assume that all ads are lying to me, and chose more focused research methods when I feel I need them.
Now, if that very simple heuristic wasn't working for me I might be pressed to spend some time making a more complex, less binary heuristic. However, the simple reality is that this heuristic /is/ working for me. It's working very well.
If the advertising industry had standards, and required products to prove out their value before being advertised, then this would not be a problem, and they would actually be performing a valuable service to society. Unfortunately, they will shill for anyone with money, and do so at such scale that the best results-for-effort approach is to ignore the entire content source.