The most defensible argument I heard for these AC portable devices are for those with breathing difficulties for AC-only CPAP.
The other situations seem somewhat illogical. If you're with a vehicle it can output electricity via its 12V DC. If you're not with a vehicle you are at home and then a much bigger UPS has more energy for less cost. If you're not home nor in a vehicle then you're backpacking so then its a weight/benefit issue and why would you be carrying an AC-recharged laptop anyway? You'd be more likely with just a phone, or a smaller tablet with DC input. The cost of these AC output powerbanks is comparing to a lower end tablet.
Clearly Anker is making these because there is a market. But for me it is a puzzling market.