The better you become at healing, the better you are at pacing your CDs and make efficient use of your healing abilities.
The more gear you have the stronger those abilities become.

That means that through gained proficiency and gear rewards you will have to heal less and less, and your healing downtime will become more and more prevalent.

That means you find yourself spamming your offensive spells over and over, unless you want to stand there and do nothing for long periods of time.

Your reward for getting better at healing is 1 button boredom.