Vans, size wise are between cars and the bigger vehicles such as buses and lorries. Unlike the bigger vehicles who are less likely to squeeze thru gaps and more likely to give a wider berth, vans are in that zone, slightly wider than cars and quite nimble so they do give it a go.
I don't think bad van drivers tend to gravitate to a particular firm. Chances are that Utility vans like courier vans tend to take more jobs in a day and we see them more often. And their routes are not the same which compounds the matter.
I pay particular attention to vans, rather unpredictable when it comes to stops, change of lanes, road conduct. And you can see many of them chatting with their workmates seated next to them as they go about their work.