I was browsing through the tags when I found this. And the questions were concerned to mechanics the physics tag is misleading and hold no purpose as there is already a site for that.
The tag exists for several reasons:
There are questions with this tag. Answered questions are rarely migrated to another site; old questions are almost never migrated. So, whatever we think of new physics-related questions, the tag is needed to properly classify the existing questions. Even off-topic questions should be tagged correctly, until or unless they are deleted.
Not all physics-related questions are off-topic here. The border between physics and mathematics is fuzzy. A question about fluid dynamics, or general relativity, etc, can be a perfectly valid mathematical question.
Apparently, you raised this question because you came across this post. You commented:
Abdullah there's a stack exchange site for physics so ask it there!
This was not a good suggestion: such a post would be immediately closed on the Physics site. In general, you should not recommend sites that you are not familiar with. If you think the question is off-topic here, then suggest it to be closed as off-topic (vote to close if you have 3000 rep; flag "should be closed" otherwise).