It's usually an objectively bad idea because you lose access to and control of your capital. Your capital turns into lazy capital when it's converted to home equity.
But because many are allergic to debt of any kind, it can be subjectively good because how you feel about your financial situation matters.
My preference is to house the capital allocated to extra principal in a more efficient account where I retain control and access… which could be used to pay down mortgage principal later if needed.