Because nothing about it is single-use: the battery recharges, the pods replace, and each pod holds the legal 2ml fed by a separate reservoir. The ban targeted throwaway hardware, not capacity, and big puff devices are specifically engineered to that line.
They are machine-test maximums; expect half to two-thirds in human use. The counts are still honest for comparison between devices, since every brand measures the same way. We put realistic figures on each tier page rather than pretending otherwise.
Refillable wins on pure cost; bottled liquid is a fraction of prefilled pricing. Big puff wins on convenience and flavour consistency with zero learning curve. Heavy vapers who love the format should at least look at our budget guide before committing to it as a daily habit.