Backyard stuff always gets judged harder than it should. Like my buddy fixing his car on the lawn, everyone assumed it would leak oil but it ran fine for years. That infection story is scary for sure, it shows cleaning your tools really matters. But there's a weird gap between "professional" and "totally reckless" where most home stuff actually happens. People see clippers outside and jump to the worst case, instead of a parent just trying to save fifty bucks and hang out with their kid.
Milabutler has a point about that gap between professional and reckless. My dad used to cut our hair on the porch, and the only mess was the pile of hair on the newspaper. It taught me that careful work is what matters, not the zip code.