Currently the notification inbox (or whatever it's called) icon will show the number of PR that is waiting to be reviewed, and that is great. Email flying around and it really helps to focus on what PR still outstanding and action accordingly.
However, the ones that you created and waiting for others to review, it is no reminder visible, unless you go into the notification inbox and click Created tab.

For my use case, my project team decides that if the PR is created from internal to the team then we leave it for the requester to perform the merge. We have some "auto-approvers", and at times we want key reviewer to approve prior to merging, hence this decision.

Another use case, pull request will need to be built successfully prior to merging. sometimes we have build storms where PR build won't be picked up until after half hour, and it is very likely no one remembers to merge it when it is finally built.

Hence suggesting that notification inbox should show number in red circle if there is outstanding PR to review (current state), and if there is nothing to review, then show number in blue circle of the number of PR user has created. Show no number if nothing in both lists.