We understand your concern. we are not the only coin that has premine and certainly not the first either.
As stated in the OP premine is there for promos, giveaways, airdrops, contests, marketing and to keep the lights on. We might even do an ICO if the community calls for it.
I can assure you the people that will be receiving the free airdrops a few days after the launch won't be complaining about the premines.
Premines are there mostly for the people not just the devs.
Post your BTC3 address on launch day to also receive some btc3 to get you started if you decide to come on board.
Have a great day :-)

Thank you