One aesthetic problem is that STI / ergo units tend to sit higher on the bars than regular aero levers.
Never understood this, any idea why ?
I think it's also the fashion for very low front ends to give an aero position - but that's too uncomfortable for most of the time (especially if hanging in the bunch) to the high hoods allow a normal setup for the rest.
And there's a lot of shameless following of pro-peloton looks, even though most people aren't able to use the things.
Personally I just don't have the flexibility in my back to get that low any more.
Ride it or milk it!