At 1 gallon it IS a starter. Well almost.Can I jump in? What about sub 5 gallon batches? Using WLP001 on a 3 gallon pale ale. Starter?
For that beer/yeast you'll be fine unless the yeast is very old.
Personally, my batches are targeting a final volume of 2.5 gallons (3 gallons or so into the fermenter). I don't make a starter for ales unless the yeast is pretty old or I'm brewing a high gravity beer. Since liquid yeast is a bit of a treat for me (I don't have a LHBS that is convenient to me, and I try to order in bulk online instead of batch-by-batch), I do try to stretch it out by brewing a few batches in succession. I will typically do 2 successive batches in the 1.040-1.060 range, then brew a big beer (1.090+) - all using some (or all) of the yeast from the prior beer.
For lagers, I typically make starters in the 2-3 quart range.