I want to believe some people just want to send small patches to projects when they notice something (I tend to do the same for projects I use) but my impression is a lot of them do it so that it shows up as "contributions" on the GitHub profile which they can then add to their resume (or get some other kind of street cred).

At least typos are actual fixes, far more often you get complete spam (people copy-pasting the contents of PRs and issues from 5 years ago, sending bizzare pull requests with hundred of commits as a merge commit, leaving cryptic comments on 5 year old commits). The spam reporting process on GitHub is kind of annoying to go through, but I trudge through it every time we get one of these PRs. There was one year of Hacktoberfest where some streamer told people that if they just spammed projects with 5 PRs they would get a free shirt and every open source project was DoSed by hundreds of garbage PRs made by accounts created the same day.

Personally as a maintainer, if someone is fixing one typo in order to "get started" contributing to a project I would prefer that they go through and check for any other instances of typos in the project to make a more complete fix (or even better, add a CI job that runs codespell or similar spell checkers). That feels more like someone actually interested in fixing something about the project, as opposed to sending a one-line drive-by patch to pad their resume. (I'm still happy to take the patch of course!)

There’s also a couple of video tutorials that show how to make a pr, using node or nom on GitHub, and people just follow the tutorial verbatim, not thinking about what they’re actually doing.