If you click the branches tab for a regular pipeline you get the following message...

Branches are unsupported
Branch runs only work with the Multibranch Pipeline job type. This is just one of the many reasons to switch to Jenkins Pipeline.

However the last sentence is clearly incorrect. This job is a pipeline - and I have switched to pipeline - so it can not be a compelling reason to switch to Jenkins Pipeline - if pipelines do not support it.

steps to reproduce

• open Jenkins classic view
• create an new Item
  • choose *Pipeline*
  • use the "Hello World" example
  • run a few builds
• Open Blue Ocean
• navigate to the pipeline you just created
• click on "Branches"
• Observer the error message....