Hi Desmo, most of the hearing aids we supply, unless specifically asked for by the client, we tend not to include a volume control. The technology available today pretty much negates the need for a volume control, even for entry level technology. Any hearing aid audiologist worth their salt should be able to program your hearing aids to a level where you just leave them to do what they need to do to enable you to hear well....
The exception tends to be with profound hearing loss where a good result is harder to achieve, then we quite often find the client prefers a bit of manual adjustment...
If a volume control is present we would tend to set the mid point at which the hearing aid starts up to be at an appropriate level so in most cases the client should not need to stray from this setting anyway.
Hope this helps
Regards
Paul