If a company releases new shares wont that decrease the value of the shares I own?

When more shares are available are available there is more supply. Have a higher supply drives prices down (supply and demand). So wont the shares i own go down in value or not go up as much when they otherwise would have?

I must be missing though because if this was true why would shareholders allow more shares to be released when this would decrease the value of the shares they own?

Edit: im allowed to post here but cant comment. So unfortunately i cant ask any follow up questions or answer any of your questions. My question was more or less answered though so thanks.