Yeah but it's easier to the layman to understand. Devices are in watts. If I run my 2000w hair dryer for 30m, that'll be 1kwh at whatever rate the electric company charges.
What I mean by "confusing" is that it's harder to estimate. A joule is a newton multiplied by a meter, which is essentially the work you do when you lift an apple (which experiences around 1 newton of gravity) from the ground to a table (which is around 1 meter). So using megajoules should be more intuitive compared to kilowatt-hours. What makes kilowatt-hour easier to the layman to understand is that electric companies charge by kilowatt-hours instead of megajoules.