Plugin doesnt cleanup after uninstalling

On one of the previously protected article pages there is still:

“This content is password protected. To view it please enter your password below:” which was put in by this plugin.

Also on the single site version I was trialing, it left in a pile of menu options that werent there before. Needs to be some method to clean up. Seems a common issue with several plugins.

I think they need an activate/deactivate and cleanup link.

https://ww.wp.xz.cn/plugins/simple-membership/