Ads pay the bills. Its quite expensive to run a message board, especially one this size; upwards of thousands of dollars per month. If you don't want ads, everyone needs to make regular donations to the owner/admins...or just deal with the ads.
I'd you don't sign in there will be lots more ads. We get many visitors here who never join because the site topics index well in Google. Ads keep it free for everyone, and unlike many other forums as long as I have been a member I have never been asked for a donation or to buy shirts and stickers or click a referral link.