Customer is king indeed but why they expect/want to use latest boost if their infra is old? Use the latest version your infra supports, simple!

The customer

- "Wants" "stable", i.e. the default gcc

- Doesn't care what Boost version is used

- Pays the developer

The developer

- Wants the latest toolchain

- Wants the latest Boost

- Makes money

The developer

- Accepts using an old compiler because Boost keeps compatibility with it

- Does not pay Boost developers for it

There is no single entity that wants old compiler (other than to satisfy others) and new Boost.