In fact, strictly speaking, that logo banner isn't a backdrop. And yes' it's easy and quick to put up. We do believe the band should be easily identifiable, so we try not to do without the banner. Showing the band for what it is, a pub rock band playing in pubs, in photos and videos is part of our marketing, for when we pitch to other pubs/small venues. So the logos are not just for the punters at that particular gig, but for future landlords and customers too.
The immediate problem you hit in most pubs if you want to do that is that you'd have to use an awful lot of gaffa tape (which ruins the paint and/or the wallpaper etc.), move crockery and other decorative items to other places, interfere with curtains, aircon units, drop-down screens and projectors, you name it. The managers, while usually helpful, are not always as accommodating as you would need them to be in order to make the backdrop look perfect and be worth the hassle.