If I have turned off execute permissions on hello.sh and try to execute it

~$ sudo chmod 0666 hello.sh

~$ ./hello.sh

-bash: ./hello.sh: Permission denied

I get the permission error. But I can easily override that by using the . or source builtin.

$ . hello.sh

hello everyone

What's the purpose of setting the execute permission on a file if someone can override it using the source builtin?

hello.sh

#!/bin/bash

echo 'hello everyone'