Along with corporate services, capital procurement is often the last part of the procurement organization to mature.
It’s an opaque category that doesn’t immediately get attention for a number of reasons. It’s usually non-repeatable spend. It’s often decentralized and managed by folks at the site level. It’s sometimes assumed by management that these folks know this technical category best and meddling in their business will cause problems.
Because it’s often the domain of engineering, procurement must sometimes wedge themselves a seat at the capex table.