The non-tech savvy can have someone they trust and know vet the code for them. Obviously they can't do it themselves.
Regarding rolling your own, what makes you trust the free services more than the commercial ones? Because in the final analysis it always boils down to trust. If you don't trust their service (doesn't matter if it's free or commercial), your only option is to roll you own. Provided you know how, of course.

There's obviously a market for these services or else how do you explain the success of a company like Silent Circle? (which is American, by the way...and still it seems many people are willing to pay for privacy even though there are comparable free services, as you point out)