Slightly off topic:
Why is excessive self-promotion considered "putting your best foot forward"?
I understand that you need the money, so you do self-promotion. But this is clearly not "putting your best foot forward", but a "put a bad foot (annoy other people by excessive self-promotion) forward because you need the money", i.e. what many US-Americans do is by my understanding the opposite of this life advice which they give.
You're coming off as clearly not understanding the other side here. Obviously "putting your best foot forward" is not simultaneously "annoy other people by excessive self-promotion" in the mind of a single person.
There are two different types of people, and they think of the same action in two different ways.
I could equally well ask why putting your best foot forward would be considered excessive self-promotion. Consider the example of contacting a journalist. Why would it be a huge no-no? Why can't the journalist just treat it as any other lead? Skim the email, if they're not interested, ignore or delete. That's not a significant burden. If they are interested, such emails actually help the journalist do their job, by providing ideas for stories.