Ben, I agree with you 100% (which is why I make kits with resonators).
To be fair, the following illustrates the difference between resonators and crystals:
| AWCR-16.00MD | ABL-16.000MHZ-B2 | |
|---|---|---|
| Price | $0.18 | $0.27 (plus caps) |
| Tolerance | 0.5% | 0.05% (50ppm) |
| Temp Stability | 0.3% | 0.05% (50ppm) |
| 10yr Stability | 0.3% | 0.05% (50ppm) |
The worst case scenario (end of the temperature scale, 10+ years old, and worst sample) is about 1.1% (15.82MHz - 16.17MHz) while the crystal is about %0.15 (15.976MHz - 16.024MHz). Obviously you're unlikely to see this kind of error in either component. You'd have to look it up, but I believe NASA testing showed their resonators to be within 100ppm of the target frequency from the factory. It's also important to realize these numbers are based on a perfect board layout (and capacitor matching for the crystal, badly matched load caps can severely throw off the native frequency).