Because electrons come in contact with the quantum particles that surround them.
Quantum approach to Nature requires quanta everywhere and in every dynamic possibility. This means that they must be in subatomic particles (bound), and free from space. If quantum particles exist in space free of any matter, they still have two options for their existence: to stay or move. Also, to have and not to have linear momentum.
They must move in either the transverse or longitudinal direction when they move. These photons are transversely moving. If they lose their speed, they are static quantum particles that exist in space (a vacuum) and have the ability to rotate. They also have the angular momentum according to the theorems of motion. The photon combines the properties of two quantum particles, angular momentum with linear momentum. This combination creates a transversewave–the moving transversewave.
These quantum particles create the electric field. These quantum particles’ physical properties determine the electric field’s physical properties.
Their angular momentum gives them the first property of being electric active. Nature proves this because photons were emitted by electrons and absorbed by them. The dominant property of the electron is the electric property. The electric property may also be present in a quantum particle that lacks linear momentum. They do have the electric property, so they also react electrically when they come within range of an electric charge from a subatomic particle. This is why there is an electric field around charged subatomic particles. It is the electric field which transfers the electron’s electric properties into its surroundings in our example.
You can see animated images of the entire process in my video “How Fields Work”.
Answer: Electrons create an electric field because they have the same quantum particles that make up the electron.