Hi SVANDEWINCKEL,
When the welder is looking at your drawing with the weld notes on it, how does he/she know where to weld unless you have a welding symbol with an arrow pointing to the joints to be welded? This takes alot of guesswork out of the welder's mind and let's them focus on welding vs designing or trying to figure out where to place the welds that are in the weld notes.
You may have more control over the welding if the design, detailing, and welding are all done under your roof...but interpretation comes in to play when multiple parties are trying to figure out exactly what, where, and how much something gets welded.
Just my opinion.