Pipeline is now script, that means that one part of the script (or some library) might call disableConcurrentBuilds and a later part of the script might want to reenable concurrent builds.

Right now that is not possible:
https://github.com/jenkinsci/workflow-job-plugin/blob/b7b488057d42a2c4a0f173795dd16bde3b86a3f6/src/main/java/org/jenkinsci/plugins/workflow/job/properties/DisableConcurrentBuildsJobProperty.java