My Mac isn't locking when I put it to sleep

If I go  -> Sleep or even hold the power button, my Mac goes to sleep but when I go to wake it up I immediately see the screen I'd put it to sleep on. Before I was asked for my password again upon waking my Mac. I know that you can quickly tap a key after using the power button shortcut to prevent it going to sleep and you won't be locked out, but even after having my Mac in sleep all night last night and waiting a few seconds or minutes before attempting to wake it today I'm not prompted for my password which worries me because I have sensitive information throughout my Mac.

I have just deleted everything in ~/Library/Preferences/ in hopes it would fix bugs. Was that a mistake? Could that be the reason I'm having this issue? Should I go ahead and restore my machine to prevent other weird bugs which may have come up because of that?