Don't worry there are a whole lot of jewish people that live inside a fishing line perimeter that are going to have to explain that whole racket before you get your chance to talk about soaking.
My relatively limited contact with Jewish culture has painted a picture in which this kind of technicality is, in fact, part of the culture itself. It's great
Honestly, I kinda love the whole "lawyering with God" thing that Jewish folks have going on. For any religion with restrictive beliefs, there will be adherents who will try to find loopholes. I've been lucky enough to have an upbringing almost completely free from religion (except for a year drinking hot chocolate at a Unitarian Universalist church, which is almost not religion), but I also grew up in a super Mormon part of Utah. I've spent my whole life as a bit of an outsider, seeing people pick and choose which rules to follow and try to discretely find and exploit every little loophole there is. I've always found the hypocrisy a bit unsettling.
I think I'd really prefer it if the Mormons took the same argumentative stance with their god. It would make the picking and choosing a bit less hypocritical (which might lead to more Mormons ditching some of their religion's shittiest and most regressive teachings), and there'd be a lot less shitty sneaking around.
Yeah, they don't usually encompass the whole city, just the Jewish communities. Eruvs aren't really necessary if you aren't following Halacha (Jewish custom/religious law). Plus it's a big deal if it's broken, and it's less likely to be broken if it's smaller and easier to maintain.
Yeah, they usually only put them up in neighborhoods with a large portion of jewish people since it has to be checked for contiguity before every sabbath. That alone limits how large a portion of the city you could enclose.