system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do some small electronics such as a router have a bulky adapter plug, but a large appliance such as a vacuum cleaner have a regular plug?
gpt
Your small electronic devices all need low voltage DC power, they generally run off 24V or less so they need a power supply that can take the 120V or 230V AC power from the wall and convert it into the 5/12/24V DC that the device needs.  This can be done with a wall wart(big plug on the wall), a power brick in the middle of the power cord, or inside the device.

If you want to make a small device then you want to move the bulky power supply to a power brick or a wall wart so it doesn't bulk up your primary device.

Your vacuum just runs straight off the AC.  AC runs into the motor, AC runs to the secondary motors, everything runs directly off of power provided from the wall.  Even for bigger things like a stove which may have a display, they're large enough that fitting a small power supply inside the device isn't going to require a larger device.