FWIS3

Straight borders are nice but in many ways not practical.
Think of rivers that divide areas.
IIRC some parts of the USA/Canada border they have multiple crossings on some waterways which makes it really hard to patrol or keep in check.
Likewise mountains. It's always been a tendency for borders to be drawn around geographic features that make for natural borders where possible.

Yeah, in Out of Africa (great read) they explain how at the end of colonialism a lot of European countries deliberately drew messed up borders in their former colonies in an attempt to make them week and still dependent on their former European masters and not be able to stand up strongly with each other. Gee, wonder why that didn't work out?

Had a long convo yesterday with my mom on Ukraine who knows the history a lot better than me, she says the issue is basically Ukraine didn't exist until fairly recently as a country, it was just a part of the world that Poland and Russia always traded back and forth (and Ottomans, and Germans...). So for hundreds of years there were very fluid borders, more than virtually anywhere else in Europe, you had shifting borders and nationalities and overlords, so it's no surprise there are major issues where the borders are drawn now.

I knew this somewhat (the westernmost part of Ukraine is actually populated with Hungarians, not Ukranians- my uncle was born there when it was still part of Hungary in WW2) but my mom loves history, so now I know more details about how Catherine the Great settled Russians in the Crimea and what not than I ever thought I'd know.

Hmmm... sounds like Ukraine is just as screwed up as Croatia/Serbia/Bosnia/Herzegovina.