The problem is that their efficiency at converting electricity into projectile kinetic energy is really bad (like single digit percentages bad), getting electri

The problem is that their efficiency at converting electricity into projectile kinetic energy is really bad (like single digit percentages bad), getting electrical energy and power density is quite difficult in the first place (capacitors have abysmally bad energy density compared to gunpowder), and coils absolutely hate having their current changed quickly (which you need for this to work).