Dual 2 way breather valve on evap system?

Does anyone know the purpose or why the later cars have dual 2 way breather valves on the tank vent evap system vs the single valve on the earlier units? It looks like the hose simply Y's into 2 valves and the Y's back together after. Looking at replacements while I refresh many items and the cost on the dual valve vs the single is huge!

 

RIGHT! Probably should have been more clear. The price of the single is silly for what it is. My car is a single.
$9 for the newer dual Vs $100 - $400 to NLA depending on where you go for the single plastic valve which shouldn't be more than $10 like the dual. My car is a single valve car. Scratching my chin of why I can't use a single of the low cost dual valve or use 2 of the lower cost valves like the later cars. Other than originality looking to see if there is a technical reason to stay one way vs the other.