Even employees at large tech companies or producers of high volume devices that rely on your Open Source project will show up asking questions and demanding actions, using seemingly anonymous or with personal-looking email addresses. It is a common practice to avoid using the company domain in emails to mailing lists to avoid too easily revealing their association.
Sometimes this may of course be because said employee is actually working on a side project on their spare time and truly is an individual asking for help, but in other cases it is done to hide for competitors that company X uses this project, to make the user avoid comments (or hostility) from others about company X but also to avoid it appearing as if company X that is making a lot of money of their product looking for freebies (which they might be).
Other reasons for hiding your true name and identity include people who feel uncertain that they will be treated badly or at least "unequal" if they do. Perhaps the contributor is a member of a minority group, such as one with a disability, a follower of an unusual religion or a woman in what is a seemingly male-dominated group – which might only appear male-dominated because the other women already present are using male-sounding aliases.