"valuable purpose" is correct and usable in written English.
You can use it to refer to something that has worth or importance. For example: "The charitable organization aims to provide people in need with a valuable purpose in life."
Mr. Healy asserts that watch lists serve a valuable purpose.
"Focus groups serve a very valuable purpose, and I think Bob believes that, too," he said.
Even in the new economy, unemployment insurance still serves a valuable purpose.
And yet from a distance it was clear that the protests had served a valuable purpose.
These are merely hypotheticals, and testing and experimentation are not bad – they serve a valuable purpose.
I learned that towns of every size serve one valuable purpose or another.
Yet the new novel's overstretched plot does serve several valuable purposes.
That, of course, would require the administration and Congress to lift their strictures against using any more surplus embryos for these valuable purposes.
Frills aside, it's clear that this kind of distance-neutral communication can serve two valuable purposes in a world seeking to advance the human condition without causing too much environmental harm.
Written plans and procedures have been shown to serve valuable purposes in training new organizations, individuals, and public officials for responding to these events.
Early introduction to surgical skills may serve several valuable purposes; medical students will acquire skills that will reduce their anxiety in approaching clerkships and improve the quality of patient care, and they will possibly become interested in surgery as a career.
