Steam is a valuable tool but one must recognize the limitations. For example, I can heat sterilize all the furniture in my mobile trailer, remove baseboards and treat those areas directly with chemicals, and still end up with large numbers of bugs in the glue board traps that avoided all these processes. I have been also involved in a few cases where the entire suite was demolished right down to the studs and noted that bugs were 4 feet up in the walls and inside door frames that were completely inaccessible to all exterminator tools. A steamer will never in a billion years access these areas.
In terms of field experience I had the local bug n scrub folks spend an entire day preparing/steaming a badly infested suite. I then spent 1.75 hours carefully chemically treating the suite and installed glue board traps under bed and couch legs. We started catching 400 bugs every single day and had to change the traps every few days because they were saturated with bugs. All told we collected 14400 bugs despite an experienced tech spending all day steaming and vacuuming the suite. I do not blame the tech for this result – it is a matter of the bugs hiding in areas completely inaccessible to the steamer. Steam is an excellent tool but it is not a miracle tool.
The usefulness of steam is also hampered because it is the bugs furthest from the host in the walls and door frames that are the most problematic as they leak out slowly. The bugs nearest the host in dressers and furniture are much more likely to be caught in the traps sooner. As such I sometimes wonder if we would not be better off just glue boarding and getting the closer bugs that way. The exterminator will never get them all anyways so why spend an entire day doing something that is doomed to fail?