More seats. Better range (over 3k miles for c series). Better short field performance. Overall more versatile. Same reason Air Canada is replacing their a319s and 190s with them (besides nationalism and supporting their hometown government subsidized company). I imagine the CS100 and e195e2 have similar economics.

Although similar to the e190, the e190e2 has a bunch of new parts. New FBW, new motors, new avionics, new wings. My understanding is there is not that much parts commonality between the 190 and e2 fleets. EMB kept the dumb ram horns at customers request so they could keep a transition training program instead of requiring a new initial training program that would have been required with side sticks. So there's that. But, we'd need new infrastructure for the e2s as well. Maybe not as much as for c series, but it'd still be substantial. I just push buttons though. Im sure the smart bean counters will figure out the best solution.