Bringing spacecraft to higher orbits than LEO is quite expensive and as rocket reusability gains traction, it will probably get even more expensive when compared to a standard LEO deployment since the first stage does not have enough surplus fuel to go back to earth (at least the current designs).
An electrodynamic tether is a device which can exchange electrical energy for kinetic energy and vice versa by exerting a Lorentz force against the Earth's magnetic field. Since a spacecraft using this technology would not need any fuel once it's in orbit, it would be significantly cheaper to deploy. Combined with a magnetorquer, it would prolong the lifespan of a satellite significantly.
Why is this technology not being used all the time? Are there any issues with practicality of such a system?