Paint scheme designs are most often influenced by the designs used by manufacturers. Years ago, we purchased many more new aircraft, and factories were churning out sparkling new models to fulfill that demand. Most often, design was strongly influenced by manufacturing. Straight lines and spaces between the colors are easier and less costly to lay out and paint, plus complexity in design would often cause a bottleneck in production.
When Scheme Designers was started in 1997, a key stylistic approach was to emulate airflow across the aircraft. At the time, we were mocked for going against the status quo. Now, implementation of curved lines and smooth flows has become the standard approach to paint scheme design. As manufacturer throughput is drastically lower than the heydays of the late 70s, they have been focusing more attention on aesthetics and marketing, and thankfully, paint scheme designs have become more interesting and elegant.