Precicely because the better the admin, the harder it will be to justify paying them. (This is one of those amazing contradictions which has led to engineers deliberately designing products with limited life-spans, with a complexity level so high that only the original engineers can really understand what is going on.)
A mediocre admin is needed constantly, to keep unstable software running and to do "routine" maintenance work.
An OK admin (the sort you generally get, when out-sourcing) is needed regularly. Mysteriously, this regularity seems to be a function of how much a company can pay, versus how much they are willing to pay. Of course, this is entirely coincidental. Honest!
A good admin (the sort you'll occasionally get, and might even find when out-sourcing, but it's rare) is needed seldom. The software is reliable, the security is all in place and the servers are all largely self-maintaining, though a combination of watchdog cards, journalling file-systems, self-repair scripts, and backup tapes. All the good admin should ever need to do is add/remove users (oh, wow! a lengthy operation!), or swap tapes from time to time. The only complex operation is getting the whole setup working smoothly at the start.
A brilliant admin is much the same as the good admin, only they've got a whole stack of CDs pressed for a wide range of common situations, reducing the start-up time. They'd probably also use a jukebox for backup, so that the rewritable CD is automatically swapped, as needed. (Jukebox drives are nice, but they are VERY expensive.)
Now, company X considers out-sourcing, or hiring. If they out-source, they'll get an OK admin, but (more importantly) they'll get the illusion of work being done, because the guy is fairly active. On the other hand, if they hire, they risk getting a brilliant admin. Sure, the work really WILL get done, then, but that means that they'll be paying this person to sit on their backside and drink coffee for 364 days out of every 365.
Given that choice, the bosses will feel they have no choice, but to outsource. No way on Earth will they allow a member of their workforce appear lazier than the managers. That might demoralize people.
Bottom line is this: Appearance really IS everything, in a corporate environment. Actual progress is irrelevent. That's why corporations rarely do anything useful.
And that goes back to the question of how you justify the existance of a SysAdmin. The only admins you can even hope to justify are the incompetent ones, and they're the ones you definitely don't want to hire.
About the only way you can "justify" a System Admin, in today's cut-throat world, is if the "admin" is also doing some other work, as part of that justification. Because of politics, the more "Upper Management" that work is, the better. (It prevents the "why do we need to pay this lazy slob all this money? they don't DO anything!" syndrome from corporate accountants. Accountants and financial advisors don't think in terms of prevention. If it's not there, and not being cured, it doesn't exist.)
This actually goes along with a similar paradox, in the medical profession. The best doctors in the world are the ones almost nobody sees, because they tackle why the problems arise in the first place, and so work with the patient to prevent them happening again.
However, since doctors (and out-sourced admins) are paid by the problem they fix, it's much more profitable to create problems than cure them. They just have to be subtle about it. There hasn't been a need for a single successful DoS attack, or a flu epidemic, since the 1960's. The problems exist, and persist, because those are perhaps the easiest sources of income these professions have.
(Actually DoS attacks, and virus threats, have started being replaced by mysterious cracker vulnerabilities. In all liklihood, it's because those cards have been over-played and people are beginning to ask why things haven't been fixed, already. Good question, and if it had been asked a decade or so earlier, I might even have believed there was intelligent life on Earth.)
In Conclusion: The very best admins, to justify their own existance, have to imitate the most pathetic of admins, to generate a large enough "mision-critical" and "severe" problems to warrant their pay-cheque.
It's a very, very sad world we live in. But it can be profitable, if you like acting.