For the first few years that we had cattle, I raised lawn ornaments. I didn't milk them, or eat their meat, or use them for pulling. Even though Milking Devons are extremely rare (estimated between 1,000 and 1,500), just breeding more of them is not enough to save the breed.
To be worth saving livestock has to have utilitarian value. Our Devons perform their historic functions of meat, milk, and draft. Each animal should exhibit characteristics of all three uses. The selection for only meat characteristics resulted in the development of RedDevons and the current English Devons. Both are lovely animals, but they are not Milking Devons.
Taste Devon beef, milk or cheese and you'll understand why they need to be preserved for future generations.
Working cattle, oxen and handy cows, have a future in forestry and on small farms. Draft cattle do less damage to the forest than mechanized equipment, they are affordable, relatively easy to train and up-cycle very nicely.