Let's say a startup gives the investor of round A 35%, despite the fact that it has already given 15% to the incubator and the business angel. In round B, investors will receive another 15-20%, in round C they will demand 10-15%, and another 10% will be given to employees in the form of options. Then the equity share of the startup's founder will remain just scanty, and any motivation to move on will disappear. Think carefully before giving away a significant portion of your creation.