You have to think of "Electrum" as this open source software that exists on the internet and everything it does can be seen by everyone. So it will exist until the end of time as long as the internet exists!

Probably because nested SegWit is less efficient than native SegWit and legacy types since it takes up a a lot more space (even though it has less weight compared to legacy but more compared to native SegWit).

Plus at this point which is nearly 5 years after introduction of SegWit into consensus rules, there is no reason to use a service that doesn't support native SegWit addresses because there shouldn't be any such service anymore.