echo does not do anything with standard input; it only parses its parameters. So you are effectively running
echo which, by itself, outputs a single empty line, and the standard input is discarded.
If you want to see the behavior you are trying to implement, use a tool designed to parse standard input, such as
$ pwd | cat
If you really want to use
echo to display the current working directory (or the output of another command), you can use Command Substitution to do this for you:
$ echo "Your shell is currently working in '$(pwd)'."
Your shell is currently working in '/home/username'.