Why does `cp -p` command fail to preserve ownership and permissions while copying files to an External USB flash drive with FAT32 filesystem on RHEL?

Issue

• While copying files using cp -p command from system to an USB flash drive formatted with FAT32 filesystem, file ownership/group ownership and permissions change. The option -p doesn't preserve the permissions.
• Here is the example,

[root@Administrator test]# mkdir first
[root@Administrator test]# chmod 700 first
[root@Administrator test]# chgrp Administrator first
[root@Administrator test]# touch first/file{1..10}
[root@Administrator test]# chmod 777 first/file{1..10}
[root@Administrator test]# chgrp Administrator first/file*
[root@Administrator test]# ls -ld first
drwx------. 2 root Administrator 4096 Mar  2 17:23 first
[root@Administrator test]# ls -l first/
total 0
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file1
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file10
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file2
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file3
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file4
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file5
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file6
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file7
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file8
-rwxrwxrwx. 1 root Administrator 0 Mar  2 17:23 file9

[root@Administrator test]# mkdir /mnt/back;cp -rp first /mnt/back
cp: failed to preserve ownership for `/mnt/back/first/file7': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first/file5': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first/file1': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first/file3': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first/file6': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first/file4': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first/file10': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first/file2': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first/file8': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first/file9': Operation not permitted
cp: failed to preserve ownership for `/mnt/back/first': Operation not permitted

[root@Administrator test]# ls -l /mnt/back/
total 16
drwxr-xr-x. 2 root root 16384 Mar  2 17:23 first
[root@Administrator test]# ls -l /mnt/back/first/
total 0
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file1
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file10
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file2
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file3
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file4
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file5
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file6
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file7
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file8
-rwxr-xr-x. 1 root root 0 Mar  2 17:23 file9