Landscape fabric is completely optional; some homeowners wouldn't dream of landscaping without it, but some gardeners find it annoying and say it gets in the way. Most professional landscape companies use it because it is generally believed that landscape fabric reduces weeds. Landscape fabric does help prevent weeds, but is not a completely foolproof weed inhibitor. Determined weeds may spring up in the mulch on top of the landscape fabric and make their way through. If they do, they are especially difficult to remove because you've got to wrestle with the fabric that the roots are threaded through and entangled in. If you use landscape fabric, it does have to be cut back as perennials spread and suckering shrubs grow in girth. Personally, I mulch my beds and dont use landscape fabric. I think bed maintenance is simpler without the fabric.