This. The original Steam Controller did not meet the de-facto standard baseline for controller layout established by the first DualShock[^1] that games have learned to expect and build their control schemes around.

[^1]: Ignoring the analog button - which is not part of that “standard” because the software does not even need to acknowledge its existence - and the vibrations (which many controllers have, but are not required for input to work)

The Steam Controller 2 does have everything in that layout. It’s modeled after the Deck’s layout, which is quite good.