... Right, because you can never have better things to spend your Karma on. Want a rating 3 Power Focus? 18 Karma. Rating 4 Spell Focus? Another 8. Now add 5 for Mentor Spirit, and we're up to 31. Maybe you want to grab Focused Concentration, too, or a couple of Rituals or Preparations. A Mage has a lot of stuff to spend Karma on, and spending that Karma on Power Points instead directly makes you a worse mage.
a) You're ignoring the benefits you can get from the adept powers
- you could spend 12 karma for 6 points in physical stats, how much would that cost you in karma?
- you could spend 7 karma on improved reflexes, which frees up a spell slot so a net of 2 karma to have it always active without sustaining, which means no sustaining focus needed either, and to sustain a force 6 spell for those 3 dice costs 12 karma for a rating 6 sustaining focus, so the mystic adept is well ahead on that (5 karma for the spell, 12 for the focus)
Or looked at another way focused concentration lets you sustain a force 6 improved reflexes for 24 karma, over 3 times the cost of having it permanently on and it means you can't buy other qualities, to sustain armor rating 3 takes 12 karma.
You have a bit more flexibility with the quality but you've got opportunity cost and for 12 karma you can effectively have a force 6 spell (Increased Reflexes) 7 karma, Astral Perception 2 amour and 3 points of permanent armour (or 1 point body and 1 point permanent armour)
how does 2 karma for Astral perception, 7 for improved reflexes 3 and 3 additional reaction or body compare with what you get from anything else?
note that you're limited to 25 points of positive qualities and with negative qualities that could leave you with 38 karma available for everything but adept powers
Maybe you pick up some adept powers that let you buy less spells, maybe you depend on a couple of spells to free up for additional adept powers.
You can't do everything as a beginning mystic adept but then again you can't do everything as a beginning mage either and there are certainly things that a mystic adept can do a hell of a lot cheaper than the mage (boost skills, boost physical attributes, get native initiative boosts, bonuses to social effectiveness if you're looking at doing some face work),
Rapid Healing and/or Pain Resistance can stop penalty dice which might be more of a boost than a power focus at some stage (and note that drain can't be healed other than by time),
Also note that you have the option of picking up qualities, focuses etc in play, it's fairly tough to pick up a natural +3 dice to initiative any other way than being a mystic adept.
b) You don't need to spend much karma on power points to get benefits.
So you could spend 2 points on Astral perception and 3 points of karma for +3 dice on Perception and Assessing.
That's a lot cheaper than you can get 3 dice on 2 skills normally...