Writing checks is a labor-intensive process. You have to grab them, write everything properly, fill in the numbers, and sign. Then you may have to provide ID and add more information that the cashier requires. Hopefully nobody behind you is in a hurry.
You can move faster by using a Debit card. When paying bills, you can get the bills paid more quickly online - with less errors, and at a lower cost (see previous pages for details).
Further reading: