Modern flash drives have a built-in "retirement plan." When the NAND flash memory cells wear out or the controller detects a hardware failure, it often switches to a permanent read-only mode. This is a safety feature to let you save your data before the drive dies completely.
There are three main reasons a drive enters this "read-only" state: usb-write-protect
Windows can set a "read-only" attribute on a specific disk via its registry or command-line utilities, often as a result of a crash or a specific security policy. The "How-To": Removing Write Protection Modern flash drives have a built-in "retirement plan
Some older or high-security drives (like certain SanDisk models) have a tiny physical toggle on the side. If it’s flipped, the drive won't let you write anything. usb-write-protect