You say things like "1-2 spells for a run isn't doable" and "you need to be able to make them past security" as if they were objectively factual.
They're not. Also note that in this edition preparations can go thru mana barriers just fine (so long as they're not currently sustaining a spell). Per pg. 161:
Mana barriers on the physical plane are invisible
(except to astral perception), but they act as
solid barriers to spells, manifesting entities, dual-
natured entities, spirits, and active foci.
Is it significantly easier if you could front load a bunch of spells while huddling in the janitor's closet while taking a 5 minute breather? Sure. But that's clearly not the design goal for preparations.
Lets say you are making an alchemist, not a full mage just a alchemist. At 1-2 spells that may or may not come into play, you aren't a alchemist, you are a unaugmented dude with a gun.
Ok, sure. You're only able to do most likely 2 spells for the action phase of the run. Or, if you deliberately pick low drain spells, maybe more. Certainly no more than half a dozen, granted, before the first preparations begin running out of the best potency band. And necessarily, the enchanter has to pick all those spells ahead of time, probably spending resources on reagents to boot, to get those spells. So, why indeed, would anyone want to play an aspected enchanter instead of an aspected sorcerer or even an aspected summoner?
1) Well, first of all maybe you don't WANT to be OP. There are those players who enjoy logistical challenges, and this archetype provides it.
2) Maybe your group doesn't play pink mohawk. Enchanters fit in much better in a black trenchcoat playstyle.. where you abort and fall back to try again rather than just breaking out the miniguns and fireballing everything when security spots you.
3) Maybe you don't MIND being a "mundane with a gun" who can do a little bit of magic. You can still astrally project and perceive, which are both huge abilities to have. And of course, unlike aspected sorcerers and summoners, you can actually MAKE foci. Maybe you like the idea of being a crafter in downtime, providing tools to your "more powerful" aspected teammates, or just making phat nuyen playing the Talismonger game.