They help significantly to combat the heat island effect in cities and provide shade and cooler microclimates for people to shelter in when it's hot.
Just try going to a shady tree-lined path vs. a paved treeless path on a sunny day and you'll be pretty clear on the meaning of this meme.
So yes we can't stop global warming with trees alone but we can mitigate the local effects of it all while providing habitat for birds and shade for people and lots of other benefits besides.
This article has a pretty good review if you want to take a look at some of the benefits! https://www.mdpi.com/1660-4601/17/12/4371
And here's a more plain-language website about urban trees: https://www.climatecentral.org/climate-matters/the-power-of-urban-trees-2023
They don't. My local shop has a waiting room with coffee, sodas, Wi-Fi, and seating/desks. Plenty of people (myself included) bring their work with them to the shop while their car is fixed. Also I've definitely seen people driving around loaner vehicles from dealerships before which is kinda a solution?
But you're right that it sucks that our society has designed places where it's impossible to get around without a car. My car shop is a short bus ride from my house or a slightly longer walk. If I take my car to the dealership, which is farther away, home is a bike ride away or I can go to the shops nearby. I'd guess this is the case in most denser urban areas except maybe some US cities which are just terribly laid out.