why do I suck at slap jack

I was out with friends last night. we went to a bar, as you do...and dorkily played cards all night. ERF or slap jack is the most addictive game I have ever played, and I couldn't be worse at it. It seems like a basic concept...slap the jacks. I never even came close to getting one. Once I did slap at it, of course the other two peeps had already both slapped and removed the cards. I slapped an empty table people! speed and accuracy apparently not my forte.