I'm connected with organisations which sometimes have meetings involving people from out of London - including from abroad. I always used to keep a few of the London bus maps - especially the central ones - for anyone with time to spare in London who wanted to get around other than by tube. But there have been so many changes - ie cuts - in routes lately that my existing maps are really too out of date to let a non-Londoner loose with. Result - some people are deterred from having an outing while they're here because they simply can't plan anything easily without a bus map in front of them. [I know what it's like, having not long ago been in a major foreign city which had no bus maps; so I spent less time doing things there (in fact less time there), and no doubt local businesses lost tourist custom they'd otherwise have had.] Mike Harris's ones are great as a reference - he's an absolute hero for producing them - but they're rather too small/cramped to use easily whilst out and about. And of course most visitors would never come across them anyway.
It does seem that TfL are running down the bus service almost deliberately; all the regular bus journeys I make around the centre are now much slower than they used to be.
Another map-related problem is that the big spider maps at bus stops no longer have a table in the corner listing all the routes with their destinations and the stops they serve. Crazy!
There are some TfL tourist publications which include a "tourist bus map" which is just a tube-diagram-style "map" of the central area, but showing only about 15 or so of the 150 bus routes that tun in the centre. It might be useful if you want to know which route will take you past the Tower of London, or whatever, but - as someone living near a major central London tourist destination - I've lost count of the times I've seen tourists at a bus stop trying and failing to marry up what's on their "bus map" with the route(s) at the stop they're at. (In a period I was on foot around the centre most days rather than mostly on a bike, I'd encounter this situation several times a week.)
Visitors think that little diagram is the central London bus map; but the use of it is more than just not helpful - if they try to use it to move efficiently around London, as opposed to wanting to see a couple of sights, then it actively misleads them. There was a time when, if I saw this situation and I had a common language with the tourist, I'd try to explain that what they had wasn't really a bus map, and dig a proper one out of my bag and give it to them. I had many instances of bewildered tourists who were extremely grateful. But of course, with no proper maps existing now, I can't do that. But I still frequently see tourists in that situation.