The 7 axle semi truck trailer is really only used in Western Canada and some Western States. Common applications of this truck combination are in the oil and gas industry, and for specialized applications such as tankers or bulk haulers in Western US states, where weight increases are tied to the bridge formula weights. This is a great truck for off-road applications, allowing an increase in gross and axle weights, without having to deal with drop and steer axles on the trailer. However, some jurisdictions require the tridem group on the tractor to have all powered axles (no drop axles allowed). This leads these trucks to be much more expensive to operate in terms of fuel and maintenance.
