[Quatar]

I see that Quality in a lot of builds here.

Up to rank 5 it saves you 5 karma. Then it costs more and eating up those savings, and by rank 8 it's more expensive now than without.

So, am I missing something, or why do so many people have it?

[Rift_0f_Bladz]

Because most characters for Missions style games will never raise there skills above 6 that have skills already at that level. Instead they generally pick up more additional skills to help round them out. Think of the show Leverage. Park originally had no abilities as a grifter, but over the course of the series, she leard some of the basics.

[gradivus]

These are for people who have a limited amount of skills at chargen.
Usually they have 6 skill points in the main skills they use and pretty much nothing else.
JOAT then lets them build up lots of skills at low levels...

so a face with 24 skill points might start out with just Pistols 6, Negotiations\Bargaining 6\+2, Con\Fast Talking 6\+2 and Perception 4. After chargen he builds up sneaking, gymnastics, leadership, disguise, impersonation to 5. For two points he can build those 5 skills for 125Karma. Without JOAT it would cost 150 or 23 point saving. Additionally, there are plenty of skills that can be bought at just rank 1 saving 1 point each, Arcana for Adepts, all the Technical skills so you can help your teammate on extended tests, and of course Pilot aerospace and aircraft because you never know when that space shuttle parked on the launch pad is going to be your only means of escape.

[Facemage]

I agreed with gradivus and Ritz_Of_Bladz. Moreover, there are some builds which never needs higher than 6 in their skills. For example a mage. For him the best use of karma are a) low level skills b) foci c) magic value d) spells e) initiations and f) quickening costs. Maybe some attribute points and later an ally spirit. I think that a typical mage can get ridiculously high dice pools with power focus, high magic and spirit aid.

[Whiskeyjack]

Because most characters for Missions style games will never raise there skills above 6 that have skills already at that level.

Not just Missions.

There is very little mechanical incentive to raise skills above 6 for any character. The cost-benefit ratio doesn't favor it at 6-7 and gets worse from there. Archetypes that depend on karma for advancement (Awakened, Technomancers) have much, much better things to spend Karma on (initiation/submersion, foci bonding, spells/CFs). A level 1 Power Focus is a much better investment than raising Spellcasting from 6 to 7, and people rarely buy the level 1; you may as well just save for the level 3+.

Archetypes that depend on nuyen to advance (sams, deckers, riggers) would benefit much more from the karma-for-nuyen trade than raising a skill by one point.

As in 4e, you largely start with the high-level skills important to you, because that's what justifies you getting paid for criminal activity from run #1. Raising the skill cap to 12 was done, I think because in 4e you could start at the top of your field with a 6, and I don't think the writers liked the notion that any character would be at the objective top of their field starting at chargen. Raising the cap to 12 shows you have a long way to go to be at the top of your field in a skill, but the mechanics certainly don't incentivize actually truing to get there.

JoAT is great for picking up a bunch of skills at 1-2 with karma, which is even better for numen-dependent Archetypes because they usually have high Attributes boosted even higher with ware. Pilot Ground 1 may not look like much but when your augmented REA is 10, you just got a pool of 11, which is more than you will ever need unless you try to do cray maneuvers (which you want a control rig for anyway).

JoAT also lets you short skills to a lower priority and pick up the tertiary (but occasionally useful) slack in play on the cheap. Like Arcana for Awakened. It's basically useless except for initiation. So you want to get 1 before you have enough karma to initiate, then after a couple initiations you want to boost it to 2 and maybe buy a spec to ensure you keep making your rolls.