I have a gas fireplace with no logs. Do I need to put in the (fake) logs for it to work effectively?

We purchased our house last summer and it has a fireplace with no logs in it. It has gas however, so I am wondering, do I need to put in some fake logs for it to work well? We tried running just flame from the gas, but it didn’t seem to warm the house up much at all.
If so, why do I need the fake logs?