Why is a city block longer in 1 axis over another?

The answer has a connection to the width of the road servicing the block. For nyc, to go with the longer part of the block, there's an inverse relationship to the width of the road. So in nyc, on the long side of the block, the road is narrow. Just imagine if the long roads had more width; it would be impossible to go crosstown. That's because the smaller width streets would be clogged up with people's business (double parked cars, etc - whatever reason ppl have to stop/park their cars) & ppl trying to get crosstown. At least, if it was traversal, a driver has more options to go crosstown rather than being funneled thru fewer cross streets.

Note: the stoppage aspect of cross-streets would still be there. Rather, it would just be easier for those in constant motion going cross-town and the actual usage of the available bandwidth of drivers going uptown.