I wouldn't really say they're terribly inefficient. They've got a lot of practical uses.
And I wouldn't say cars themselves cause the deaths. Its the dickheads who drive the cars. Much like how a push biker, who looked like he was about to stop at some light that he was supposed at, decided to just go faster and swerve straight in front me, causing me panic, slip my bike into neutral when I wanted second, put on my revs whilst being in neutral, then having to aggressively throw my bike to the left, just so that I wouldn't plow straight into him. This cause me to have to the thread the needle between him and another push biker who I could've easily hit as well. If I were in my car, chances are I would've clipped either of them, and it would've been their fault. Not the cars.
Whilst they can take up a lot of space, it should be important to know that quite a lot of the time, cars here drive over roads that would've originally been planned for horse and carriages. And only really just adapted for cars. You can see that on UK country roads.
Do you mind me asking where you're from? I haven't really seen anything like the last point where I'm from. Quite a few places are pedestrians and push bikes only. With very few exceptions. That could also be because you rarely see big cars here. This also applies to taking up excessive land.
I do believe that public transport should be a lot better. I live in a small village about 10 miles from the nearest city. And I work in the city centre. My only options are either pray that a bus actually shows up and isn't late, or take my car to the tiny not really built for cars alley and risk scraping it. The other issue with public transport is, if I have to try to get to the very back of a bus, and pray that no one sits near me, or sit in a place I will feel extremely uncomfortable with. Both of these options mean that I need to have something I can squeeze the shit out. And shelter myself in and try to be as invisible as possible. I do not have these issues with cars or motorbikes. Cars because I'm in my own personal space where I feel a ton more comfortable, and the bike where it lets me hide the entirety of my body, again, making me feel a lot more comfortable.