Any product worth seeing/writing about/using has to be attention worthy enough in the first place, and then competes with other products for attention. Just like if two hot dog stands compete on the same street and one leaves. If the remaining hot dog vendor produces the ugliest nastiest worst tasting hot dogs, he does not capture the rest of the market afforded by the absence of a competitor. But if they were the two best hot dogs stands in the city, people flock to them and their market size actually grows.

It doesn't have to. Yes, an endeavor may fail to capture any attention, but in that case, it hasn't gained the person any social/track record capital.

If you don’t like that example, pick another: learning a programming language. What is lost by me learning a new programming language? It takes time for me of course but that time would have passed anyway.