How you chose your healing job.

Initially? I thought the fairies were ugly and though I tried AST when it came out because of its aesthetics I couldn't stand dealing with the RNG cards. So...WHM it is.
Real reasons? My heal style is reactive, I love perfectly casting a heal that lands just in time to pretty much negate a tankbuster/raid wide damage and the sound of Holy is like music to my ears. Its also great to startle your FC mates when you know they are tabbed out with headphones on. *nods sagely*...also sliding through the middle of your party while you twirl about during Assize's animation and ensuing sparklies.

I'll be honest here, I originally took Scholar because it was also an easy way to level Summoner. *prepares for the hate*

However, I also played the other healer jobs a bit and found out that Scholar fits my healing playstyle more. You see, I find it difficult to more actively involved in healing like White Mage and Astrologian are supposed to be (that, and I tend to mess up Stance Dancing). I find that Scholar is more lenient in what you can do, allowing you more room to observe the party while still actively participating in the content. It's somehow easier to keep up everyone, I only need to throw out the occasional Adloquium/Succor for mitigation (that said, I hate tanks that pull mobs from boss-to-boss, Scholar has a harder time healing big pulls imo). It's why I like Scholar, and occasionaly play it when I don't feel like playing Bard.

I knew I want to be a healer since the beginning so I started as CNJ to become WHM later. Partially I also loved the choise due WHM having become so iconic for FF and the 50 armor of them you can see in the character creation screen is spot on with the white robe with red saw line. I would have liked a healer that's slightly more HoT based, used to be a druid long long time ago but took what I got. And I've learned to love WHM healer heavy style that can go boom just as easily.

started the game as CNJ and began to love it quickly. this stuck with me, even after getting all healers to 60, WHM is still my most beloved main
some change of pace as SCH/AST from time to time is nice tough

Before I subscribed to the game, one of my friends was playing it.
I asked him about the different class, and when I learned about a pet class (I love them) that can also heal, my choice was made.
Started the game as ACN with SCH in mind, never left that path. Even with all the class to 60 now, I still play SCH for everything.
I really enjoy the fact that you can dps pretty well, must play strategically and must know the limit of your heals, fairy and tank to be truly efficient.
Even after more than one year playing it, I can't get bored with it.

I played SCH mostly due to their sheer demand in raids and other difficult content. They are OP with how good they are at being jack-of-all-trades (which, I think, is partially the reason every group has one as mandatory).
I play WHM when I feel like screwing around because it's toolkit is simple and it doesn't require as much though as SCH. Since I retired from raiding though, been playing WHM a lot more frequently as of late.
I'm leveling AST now for shits-n-giggles and I'm liking it so far. Not sure if it will replace my SCH since Nocturnal stance leaves much to be desired, but I have a feeling it will definitely replace WHM as my "I'm bored" healer since it's basically WHM + cards when in Diurnal stance.

In the game I was playing regularly before playing this one I played a Healer/Support hybrid class so this time I wanted to go with an all out Healer class so picked WHM. Plus SCH's old endgame gear was really ugly lol.

During beta the only two classes I was drawn to were pugilist and arcanist. While I'm at heart a monk main I became highly attracted to the playstyle of scholar since I always found WHM playstyle very boring while leveling. Honestly if Scholar weren't even a healer role I prbly would've never picked up healing. Tried out AST come Heavensward and quickly lost interest in playing around with cards (to this day still dislike it's design with Sects too).

Played WHM after NIN to try healer. Then tried DRK to understand tanking better. Next tried SCH then played BLM. Now I'm on AST which I have up-to-date gear and most likely my final healer choice. You can say I made my decision after playing as many healer types and jobs to 60/endgame/raids as I can to see how everything works together. No regrets no doubts.

I play all three because they all have their part and because i looooove having people fate in my hand and crush the one that try to come for me...
And also because my static did needed à healer at HW and I was the only one DPS that also master the way of killing... I mean healing