[Jblx2]

- Risk mitigation. Even if you are 90% sure that things will go up and to the right, it still might make sense to cash out a bit as insurance. Especially if you aren't giving up any control

- Buying allies. If you make a lot of other people rich, they will probably become your biggest boosters. Might not be a bad idea to have some rich allies rooting for you. And you might need some political favors in the future.

[FloorEgg]

Also it's a race, with theoretically exponentially compounding gains to the winner(s). So trading 10% dilution for capital that will exponentially compound, may mean that e.g. a 10% dilution now results in 50% greater market cap in 5-10 years, or 10% dilution now means the difference between winning or coming in 4th, which could be a 10x or 100x difference in market cap.