Just guessing here, I'm left handed also. I don't trust myself to cut a piece of steak using the knife in my right hand. So, after cutting with my left hand, I put the knife down and use my left for forking.

Or, it could be what my English son-in-law does, he uses his fork and knife, in different hands to aid in pushing food onto his fork. (He's right handed, not that it matters in this case.)

That and you hold them in your fists or like a pen, rather than the European manner of holding cutlery.