I agree, but looking at a synoptic chart will, as you say give you an indication of how the surface winds may be. If you want to know more detailed information, then only a METAR or TAF etc will give you the precise wind velocity for a particular airfield. Lines on a chart are subject to all sorts of things, including the quality of the toner cartridge in the photocopier, so its ok for a rough guide for a wide area, but certainly not to be used for flight planning.