Why does all assigned apps are automatically considered as Mandatory apps?

Hello jimmytrivedi, 

If you wish to only make the app availbe in the Company portal, then you'll have to add the user group as shown below.

As if you want to push the apps to be installed during the user enrollment, then ''requried'' would be your choice. 

Here is the difference between all assignment

Assign apps to groups in Microsoft Intune | Microsoft Learn



Best regards
Shady Khorshed