That's unfortunate. We have 3 kids, and we're specifically moving down to the Model Y from the X, because it has one. We only plan to use the 3rd row for traveling...as we'd like to be able to separate the kids when they're in the car for long periods of time. Dropping off at school, or errands around town, they'll all just share the 2nd row.
I get that not everyone minds driving around in vehicles with poor mpg, but the idea of driving around in a suburban or minivan just because you have 3 or fewer kids, doesn't make much sense to me. Road trips have been completely fine with our family of 5 in our MX, and I expect that with a hitch mounted cargo box on the MY, our trips will be just as comfortable...and it'll be easier to park 95% of the time.