The fruits of labor grow ever higher. By which I mean: In the early days of a startup the problem space is ripe and plentiful, the impact you can have is outsized, and the pool of people with which to share it is the smallest it will ever be.
As a company grows, all three of these factors are subject to strain. The problem space becomes sparser, outsized impacts are recognised further up the ever-growing hierarchy, and the pool of people with which you're sharing your impact becomes larger and recognition becomes shorter lived and more diffuse.