That behavior has purpose. Some default WordPress widgets use unordered lists, that’s why bullet points are disabled for unordered lists within widgets.
You can try to enable bullet points for Text and SiteOrigin Editor widgets using the following CSS code.
You can add CSS code to your site with Simple Custom CSS plugin (just copy CSS code and paste it in Dashboard → Appearance → Custom CSS after installing and activating the plugin). Also you can add CSS code directly to
style.css file of your child theme.