It's kind of a sad parallel to the incentives and economic realities that make your favorite local boutique or art shop get replaced by a Bank of America branch.
Not only is it hard to compete for space/talent with their money, they are additionally incentivized to aggressively expand because it's defense against good people/locations going to competing firms.
We like to fantasize that the basic currency of power in silicon valley is meaningful user delight, when it's really just a narrow kind of user attention hack...
...the kind that cheaply and emptily occupies Facebook and funds billionaires' pseudo-noble vanity quests against the same purveyors of cheap clickbait that make them their money in the first place.
Instapaper can't spam my attention like Pinterest can, so it and all your Pinterest joy are living in borrowed time.