that would make it easier for someone to block, thus defeating the purpose of the ad, and reducing his revenues.
Those people who block ads (like me) wouldn't use the ad's service anyway, as they tend to ignore ads. So there's no appreciable loss in revenues, and a (admittedly modest) saving in bandwidth - which I believe is paid by B&H or the ad distributor.
I personally prefer google's text ads, which are unobtrusive and relevant. I quite often click on google search's ads for the latter reason - something I never do with banner ads even when they creep through my ad blocker. For this reason Michael might want to look into that as a potential revenue source as well.
FWIW, I'll make sure to click on that ad before I order from B&H, as that's an easy way to support LL.