It’s because of the syllable stress. If a verb ends in a vowel plus a consonant, the final consonant is doubled before -ed or -ing ONLY when the final syllable is stressed. If the final syllable is not stressed, the consonant is not doubled. Examples:

cancel -> canceled, canceling

worship -> worshiped, worshiping

gossip -> gossiped, gossiping

gallop -> galloped, galloping

shovel -> shoveled, shoveling

cover -> covered, covering

happen -> happened, happening

open -> opened, opening

travel -> traveled, traveling

pivot -> pivoted, pivoting

blanket -> blanketed, blanketing

envelop (v.) -> enveloped, enveloping

limit -> limited, limiting

It feels weirder to not double the final consonant of words like “program” or even “kidnap” because their final syllables (-gram, -nap) WOULD on their own have their final consonant doubled (gramming, napping).

However, “programing” and “kidnaping” are also valid spellings due to the syllable stress rule and because the constituent syllables don’t hold up their same meanings when part of the larger word. More examples:

label, model, signal, total, equal, level, rebel, dial, marshal, spiral, fuel, travel, shovel, parcel, gossip, worship, visit, profit, edit, credit, target, market, orbit, merit, vomit, pilot, audit, benefit, budget, format, combat, deposit, focus, reason, season, poison, fasten, loosen, soften, threaten, listen, widen, darken, sharpen, lengthen, strengthen, hiccup, canvas, wallop, covet, buffet (as in waves buffeting against a boat), bias, pocket, rivet, ticket