It depends. For operations or aggregates on a single field, it improves cache locality, whereas if operations act on all, or most, fields of the struct, it hurts cache locality. The exact same tradeoff differentiates OLTP (transactional/row stored) databases and OLAP (analytics/column stored) databases.

You wouldn't typically use this when you need lots of random accesses, but when you process the data sequentially.

It also simplifies and speeds up SIMD loads and stores, because you can load/store entire SIMD registers with a continuous, non-strided memory access.