Vorlauf does help make for clearer wort. It may not even be a normal step in BIAB, but in three vessel rig with fly sparging, I always do it to clear up wort and get mash bed primed for sparge. This results in little or no grist getting out of mash tun and into pump and torpedo screen in BK during sparge.
As to whether clear wort is necessary for good, clear beer, probably not, but in my opinion it helps make traditionally clear styles more to my liking, possibly resulting from less protien or something in the fermentor. Most likely less difference in heavier bodied beers, or hazy types.
Edit; Does not pertain to clear worts, but another reason to vorlauf, or recirculate, is to equalize temperature in mash for better conversion. Again something that might not apply to most BIAB rigs, as there is usually a smaller vessel and volume of mash involved.