When designing small or micro layouts, you can cut down quite a bit of space by getting rid of continuous running and doing, for example, a simple terminus or very small yard. However, consider how versatile the loop is, and how much is sacrificed by its removal.
For starters, it's probably our mainline. Trains will usually take a few laps around the loop going from "here" to "there".
Secondly, the loop can easily also be our runaround, when we have stubs pointing in different directions and no passing sidings. This isn't prototypical, of course, but then neither is the loop itself!
Finally, the loop is for continuous running, when we want to showcase our layout or just watch the trains run.
When you remove the loop, you're removing quite a lot.