@Background Pony  
It goes beyond his job, and for the record while assistant may not be the most difficult of positions its far more than the CMC can claim. Plus its one that gets him sent to Canterlot, by himself, as part of his duties on occasion.
 
They got o school, he doesn’t. They hang out with each other/other school age ponies, he hangs out with the mane 6. They go Trick-or-Treating on Nightmare Night, he goes to the festival. They always stay home when the mane 6 leave town, Spike occasionally goes with them, and when he doesn’t he’s left by himself when the CMC obviously would not be.
 
The only reason people started pairing Spike with the CMC was because he was a left over when they started deciding which of the mane 6 would be paired together. That’s where Spikebloom came from despite never having any real interaction 62 episodes in, when people started pairings she was the only other ‘young’ character that had really been shown.

@Itsthinking
 
One, this is before S2, dos, Zecora’s Cutie Mark (?) is on that potion.

@Sjogre
 
Assistant is not strictly an adult’s job. And dragons don’t have Cutie Marks, so the CMC don’t have anything to do with him.

@Starly
 
Because he has an adult job. He’s nowhere near as young as the CMC, nor has he ever been treated as being close to their age group.

@Starly  
Some would argue that he may be a baby dragon and ages slowly as a dragon, but if he were a pony he would age a bit faster.

@Starly  
I’ve always interpreted him to be slightly older than the CMCs. Asumming Twilight hatched him when she was the CMCs age and she is college age right now, he’d be like 10.
 
I think we’re missing the point of the picture: Twilight was stupid enough to give AB a book of potion recipes. Again.

@bustoblaster  
Not like that stopped anyone before.

@Starly
 
Because shipping.

Color >>45681

A more accurate design of a ponified spike.
 
Why do some people make him a stallion anyway?
 
he’s a freaking baby dragon.