Riffless chord strummers with lots of songs in major keys equates "electrified folk music" in my book. It's what girls like, loud vocals, strummy guitar, no riffs to get in the way and music not too dark.
But Del Amitri are pleasant to listen to and know a tune or two, just not strikingly original if I may say so.
But we all come from somewhere, and in my case I was of course weaned on a certain type of late 60ies/70ies rock where the first few seconds are generally determined by a sequence of instrumental notes (guitar- or keyboard-played) which are the signature card of the song - think of Alice Cooper's School's Out, Steppenwolf's Born to be Wild, Cream's Sunshine of Your Love, The Who's I Can't Explain, The Stone's Brown Sugar, The Door's Light My Fire, Hendrix' Spanish Castle Magic, Ten Years After's I'm Going Home, Black Sabbath's Sweet leaf, Free's Alright Now, The Beatles' Come Together, Deep Purple's Smoke on the Water, Bad Co's Can't Get Enough, Uriah Heep's Gypsy, David Bowie's Jean Genie, Mott the Hoople's All The Young Dudes, Argent's Hold Your Head Up, Zep's Kashmir - the tell-tale riff. It's a characteristic of music generally termed as rock or hard rock - but not always: think of Stevie Wonder's Superstition - and of course it is loaned/ripped off from the blues.
It's gone out of style - the last really riffy commercially widespread song I can think of was Lenny Kravitz' Are You Gonna Go My Way with its bow to Hendrix (and that was some years ago).
Playing signature riffs seems to be these days a hallmark of either bands on the Classic Rock circuit or of young bands in the retro vein niche. Everybody else tries to do without as far as chart success goes.
It's something I largely blame U2 for (and I'm only half-joking), the Edge forsook (I had to look up what the preterite of forsaken actually is, "forsaked" didn't sound right!) the guitar riff and made mere chord playing with some echo and delay trendy.
While I'm writing this, I'm listening to one of the more recent studio albums of Albert Lee & Hogan's Heroes.