It is not essential in any way else i would not be getting harvest after harvest of different plants at the moment
If you are growing new strains then you will have to wait for burnspots for you to know what EC is too high, it is more accurate than knowing that 40ml is too much, but the point is this increased accuracy is totally unnecessary.
Your idea of new users overfeeding because they do not know what the ppm is hogwash. If they are overfeeding, it's because they are overfeeding, knowing the ppm will not stop them overfeeding, as they will not know what ppm constitute overfeeding with this plant. They can either do it the traditional way and simply drop the amount of ml per litre, or they can get fancy and use an electronic meter to tell them that they are feeding it fewer ml per litre. You seem to be failing to understand that a ppm reading is little different to a ml/litre reading, whether i follow the direction on the bottle which i have happily done since my first grow without issue, if i knew that the advice was 50% strogner than my plant would want it, then i'd simply adjust the amount of nutrients i feed it, i have no use for a meter to confirm what i already know.
So again, sure, they can be useful if you want to make use of it, but are in no way needed soil or hydro experienced growers or beginners. Half the growers i talk to don't even bother Ph'ing their water, let alone ECing it. So much bullshit has been put into the concept of growing, growing cannabis has been around a lot longer than digital meters have and it did just fine and still does