Why my photos refused to be deleted?

Probably you have synced these Photos from your Mac/PC though iTunes. Un-sync then they be gone.

Un-Sync photos to your device

1. Connect your device to your Mac.
2. You can connect your device using a USB or USB-C cable or using a Wi-Fi connection. To turn on Wi-Fi syncing, see Sync content between your Mac and iPhone or iPad over Wi-Fi.
3. In the Finder  on your Mac, select the device in the Finder sidebar.
4. 
5. Select Photos in the button bar.
6. 
7. Note: When iCloud Photos is turned on, no photo syncing options appear when you select Photos in the button bar.
8. Select “Sync Photos to your device from” tickbox, then choose Photos, Pictures or a folder from the pop-up menu.
9. 
10. Uncheck Sync photos
11. Click on Apply / Sync

Did you sync photos from your computer to your iPhone?

If yes, those photos can not be deleted on the iPhone. You will have to deselect the photos on your computer and sync the iPhone again.

If the photos are part of the Recents album and can't be deleted, do you have restrictions set up in the settings for Screen Time? Or is your iPhone managed by a company or has a profile installed?