Oh! Here's a rule! Let's obey it.

No! It's an USn rule, therefore it's stupid and we shouldn't obey it.

The Reason Behind The Rule:

Normal English orthography has it that a long vowel followed by a single consonant shall have another vowel after the consonant. A short vowel shall be followed by a doubled consonant before a following vowel. Thus, when adding a suffix, a single final consonant shall be doubled to protect against lengthening (lengthenning anyone?) an otherwise short vowel, e.g., beginning. The USns have decided that there is no danger of lengthening an unaccented vowel so doubling of the consonant is not necessary if the syllable containing such a vowel is not accented, e.g., traveling.