Clarification on how is the cordless electric powered machine sourcing

[abdulbadii]

How's actually the working mechanism of the cordless electric powered impact wrench or other cordless of kinds such nowadays? Why can't they bypass directly to source the mains 110/220V AC either with or without adapter ?
as sellers say 'it can't', so confusing

[Gyro]

Another incomprehensible question.

Why don't you just buy a mains one.