Welcome to the forum.
Any idea why they do so?
Because they apply the guidelines.
The fact that other app which you consider similar, has been accepted is never an argument for the review team.
You don't know if they have done anything special to comply. Or may be, they just passed by luck but will be rejected in a future update.
Anyway, you have to focus on your own app and modify it to comply or explain why you think you comply.
PS
in fact our app ui also closely resembles all 4 of them
Take care not to be rejected as spam as well.
Topic:
App Store Distribution & Marketing
SubTopic:
App Review
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