You help one neighbour with their car and it snowballs.
I used to do that for friends and family when I was in my teens-twenties but right now I hardly have time to even work on my own cars. No way I'd do it for free either unless it's family or close friends. A few times I got in a bit over my head and spent way more time than expected. I realized my time is worth more than that and when people don't know what it's like to do repairs or maintenance themselves they tend to be greedy and impatient.
Plus anything made in the last 15 years or so is just so damn complicated, I wouldn't even bother if it's more than an oil/filters change or brake job. I'm happy to do a little diagnosis though and give some advice on what's wrong.
Just because I rebuilt the engine for my 1970 Plymouth doesn't mean I can fix the transmission in your 2016 Toyota Tundra lmao.