Because that's what would fit in within 32KB back in 1983. A lot of "why did they do it this strange way?" questions can be answered by looking at the old Elite games. It made sense back then, usually for technical reasons (or because Braben and Bell were 17 year old kids at the time and they thought it would be cool), and they just grandfathered it into ED.
Microprose managed to implement ECM which wasn't an EMP, back in its old '
F-19' game and memory space certainly isn't an excuse for not doing so, all these decades later. It doesn't have to be ultra-realistic, but done right, it would have long ago given ships like the T-9 a highly useful support role, if greater module capacity allowed for increasingly powerful ECM and ECCM capabilities. Active and passive ECM would be the true counter to turrets/gimballed weapons and guided missiles.
Higher level ECM modules could also be expanded into hacking tools, allowing us to potentially do things like send false sensor readings, shut down weapons, disable weapons and so on - means of engaging targets without firing a shot). Fantasy? That's what the F-35 can do, right now! It's an absolute game-changer for warfare and this technology is going to see a lot of use, because of how it allows for plausible deniability. This has huge benefits for things like 'Powerplay', where different factions would need to task ships with politically sensitive missions.
Equivalent ECCM gets used to counter it, in turn. More powerful ECM then counters the ECCM, etcetera. Better ship reactors would also allow for additional reserve power which can then be used to electronically 'burn through' ECM/ECCM, which also then gives us more reasons to learn creative energy management ('systems' no longer applying purely to shields, but also ECM and ECCM). It's then not just a case of getting the biggest ECM and ECCM modules, for the most optimal results, but making sure you use them right.
There would also be specialised missiles which can be purchased, exclusively used to home in on active ECM (which makes sure such a ship needs at least one escort if it's going somewhere properly dangerous).
Also has obvious benefits for pirates and smugglers against any security forces (especially screwing around with sensors to keep a low profile).
And if Frontier ever expand on 'multi-crew', ECM and ECCM gadgets could hugely expand into extremely useful and fun tools. Optional, sure, but available.
Ultimately, this is what
should be used to counter turrets/gimbal weapons. Those who feel contempt for them should be championing proper implementation of ECM and ECCM. It would make fixed weapons skills a more useful and relevant discipline.
Real electronic countermeasures covers an enormous spectrum of devices and uses. The in game ECM falls into that spectrum nicely and doesn't bear much resemblance to an EMP device, it's just omnidirectional.
How? It's
literally an electromagnetic pulse. It's not something which can creatively disable or feed enemy sensors false data. How it should function is being able to do all of that, below a certain class,
constantly, once a ship enters into an area. Right now, it's a gimmick you have to time when to trigger. It's nonsense and doesn't lend itself to nearly the same kind of fun creativity legitimate ECM or ECCM abilities could do. Abilities which could be used to
enhance just about every profession in the game, which the present version just does not do.