Ask HN: Why do maintainers spend time reviewing my code?

Recently, I was working on various open source projects. Mostly I was working on issues labelled as "good first issues". Before I start working on a issue I usually take a look at the previous attempts made by other people. Usually I can find a couple of PRs or comments if the issue is older than one year. Looking at the work history usually it becomes obvious why previous attempts were not successful: someone completely misunderstood the task and went the wrong direction, someone can barely code, someone is just pinging the contributors instead of doing the actual work[1]. What was surprising to me was that the maintainers almost always found time to answer every question, review ridiculously bad and incorrect PRs and spend days communicating with the contributor (including me) to give feedback about the work, while they themselves could absolutely resolve the issue in less than an hour. To be honest I don't understand why someone with 10+ years of experience would spend time reviewing my "good first issue" PRs like they don't have anything else to do. I am trying to be useful and to learn but I don’t want to bother anyone or waste anyone’s time and that's why I am wondering why would maintainers spend their time reviewing my code? What is their motivation?

[1] https://github.com/tensorflow/tensorflow/issues/22926#issuecomment-2888463504