Because the tab lists projects you are a member of, not projects you created. If someone invited you onto their project and you accepted, that project is yours to see from then on, drafts included, and it stays there until you leave the team.
There is no separate "shared with me" tab, and there is no filter that hides other people's projects. One list, everything you are on.
Being on any team of the project is enough
A project can carry more than one team, typically Collaborators and an organization. Membership of any of them puts the project in your tab. So you can end up seeing a project you barely worked on because you were added to the studio's team on it.
An invitation you have not accepted does not count. Until you accept, the project does not appear in the tab; it sits in your pending invitations. Inviting someone to a project: what the link does covers that.
It explains your counts
The Published and Drafts numbers at the top of the tab count everything in the list, so they include work you did not start. Someone else's unfinished draft is counted in your Drafts figure. If your counts look higher than the work you remember doing, this is usually why, rather than duplicates. Why the Published and Drafts tabs disagree with their own counts covers the other reason.
Your public profile is a different matter. Visitors see published projects you are credited on, and never anybody's drafts.
Seeing a project is not the same as being able to change it
What you can actually do on a project depends on the role you hold on it. A Manager or a Team Member starts with no editing rights at all and will be refused when they try to change anything, even though the project is listed here. What each project role can do by default sets out the four roles.
Treat other people's projects in this list as read-only unless you know you were given rights on them.
Getting a project off your tab
Leaving the team is the only way, and whether you can do it yourself depends on your role.
- Admins and Super Admins can leave. Open the project in the builder, go to Team, and use the menu on your own card. You are asked to confirm, because it also ends your access. The project leaves your tab straight away and your name comes off the credits.
- Managers and Team Members have no menu on their card at all, so they cannot leave on their own. Ask an Admin or Super Admin on the project to remove you.
If you would rather stay credited, there is nothing to do. The entry is not doing any harm, and it is not shown to visitors as your own work.