I'd estimate my BMW ride success rate at 60-70%, which isn't that bad considering they only operate 1 car at a time. More detailed analysis would probably show significant difference between busy and standard periods of day. So if somebody is only flying during the busy periods, I can see why the success rate is so low.
Need to say it again - this is a nice extra perk (when it works), but there are more important things in taking care of 100-200 most loyal customers which AY fails in.