Founders and early employees contribute work and are hopefully rewarded for that work with ownership stakes in the company. Rightly so. But as the company grows, and to the degree that it necessarily hires additional employees, the proportion of ownership held by these early employees becomes undeserved (in the simple above sense of the word). Their large ownership positions remain, even as it becomes clearer and clearer that the value of the company is created by its hundreds/tens of thousands of employees.

So if you start a business and make a profit (a hard thing to do!), that is not undeserved. But if business grows and eventually the value is created by 15,000 people all together, you don't deserve 25% of it.