Of course all these primers were fitted at great expense as ornamental exentricities ... weren't they? no?
As has been stated, they are there for a purpose ... to richen the mixture to aid starting. All engines are different and if yours starts without all well and good ... or is it? Perhaps the mixture is set too rich generally and you are wasting fuel? dunno?, but it's worth checking.
Cetainly most VW powered homebuilds need priming or they just won't start (of course some have carbs with chokes so may use that method instead)
An added bonus of a primer, though not one I've had to use ... is that you can keep an iced up engine running on one! If you have severely cocked up and choked up the card with ice to the point the engine wants to quit ... you could slowly squirt fuel via the primer directly into the inlet manifold and keep it going until you manage to melt the ice! ... theoretically
IM