The point of anything cordless is how it eliminates the hassle of, well, dealing with cords. In case of a vacuum cleaner, one has to:
- pull the cord out
- plug and re-plug it
- ensure it doesn't get stuck around the corners and under furniture legs
- ensure it doesn't pull some other furniture and topple them over
In addition, corded vacuums have practically no power envelope or weight restrictions, so they end up being bulky, heavy and loud, even if the context in which they are used doesn't require the power.
Dyson cordless (I can't speak to any other) in contrast:
- weighs lot less and can be carried around with ease
- can be moved around without a second thought of where the cord is or whether it can be maneuvered in a certain way
- is a lot quieter (can be used at night)
- is instantly accessible without any setup so it makes sense to use it for a few seconds to clean something up
- can be used outside of the house where there is no power outlet - e.g. in the car in a rental apartment parking
Since I switched to cordless (which has been 6 years or so), I no longer dread vacuuming. It's actually a pleasant experience and sometimes, when I get a few minutes, I do a clean of areas that get dirty often (entrance).
The battery life and the power available have improved to the point where it's no longer something I worry about (especially for my two bedroom apartment).