is so much more intuitive to use the same lever action to go up the gears on both hands
Not just that but it means the mech spring is helping you do the hardest shift (smaller cog to bigger) so reduces the effort at the lever, thats why RR leant itself well to flappers as it was all light finger work rather than thumb pushing. It does however mean you need a system in good shape and with a strong spring to make that shift as you can’t just tease it a bit further to shift like you cna when you’ve got old gummed up cables or worn mechs.
Never got on with he flappy shifters myself, but I do miss* RR 🙁
*Although 1st gen Alfines shift that way too so I still ahev one bike where the shifting action is reversed, somehow my brain knows as soon as I’m on the bike and I can swap between bikes without getting confused.
Same with the road bike, some Campag, some Shimano, and despite the inner lever (behind brake lever) working opposite on them my brain seems to just know and shift the right way…weird