I have a footprint for my Marmot Pulsar 1P and it's thin and light and only covers the area that I sleep on. In hindsight, I shouldn't have bought it, it was one of those 'it seemed a good idea at the time' moments.
I always carry a larger area groundsheet because I like my porch or part of my porch to be covered as well. The footprint does serve one useful function, however, when it's raining it acts as a template where I can erect the outer tent first and then erect the inner tent in the dry. I can do this without the footprint as well, with four very simple pre-measured lengths of light string with a small loop at each end.