Having more money won't make the game progress magically faster. Devs don't want to have a bigger team and already work full time on it (except for Victor, the web developer). And having ads on a website where you already sell a product is unprofessional.
If you are referring current ongoing graphics enhancement efforts it might actually hurt someone if advertised too eagerly. Reason is that we don't know, may be that even the devs don't know, when the update will reach needed release maturity. It can be after 6 months, after a year or even longer time. So advertising may result false expectations among users, especially among potential new users
And more demo users buying a licence would hurt less than adverts that most people may never see due to using ad blockers.
More licenses more likely to be profitable for developers than hoping for thousands of users to click on an advert and get a small percentage of 1p / 1c per click.