Does the doctor pull stitches out from gums after extracting wisdom teeth?

That depends: That depends on what type of sutures are used. There are two basic kinds - dissolvable and silk. Dissolvable do not need to be remove as they dissolve on their own after a few days. Silk sutures do need to be removed by the doctor. Which type they use depends on how strong a suture they feel they need for your situation. Silk sutures are stronger.

Sometimes: If silk sutures are used, this do not dissolve and must be removed after 5-10 days. If gut sutures are used, they will usually fully dissolve and require not removal. Sometimes the dentist will remove them when they protrude and irritate the tongue.