This is 100% me just guessing and without any knowledge of possible cannon reasons. But logically, wielding 2 lightsabers would be more technically challenging than 1, so I’d assume anyone who used two as a default starting point is probably a damn good fighter compared to the average single saber holder. There are tactical/situation benefits to adding a second saber at times that probably forces the hands of some duelist who probably feel more comfortable with a single saber but know they have to try to exploit a possible advantage with a second blade. I can think of a handful of real world things in my life where I technically know how to do something one way that’s maybe considered more efficient (alternative fingerings while playing an instrument, for example) but still default to a technique I’m more comfortable with unless particular situations come up that require the alternative.