John, I drove I-15 between Vegas and L.A. a couple of times, and there was always traffic.
My girlfriend at the time and I had a bet as to which was quicker. Her parents lived on Balboa Island. I took her to the airport, then drove down and she flew. By the time she went showing up an hour early (recommended at the time) through check-in (you had to do it at the ticket counter in those days), baggage pick-up and all the rest, I think she'd only been waiting at John Wayne for 30-ish minutes when I rolled up.
And that was when the limit was 55 (I may have been doing 60). When that got ditched in the mid-90s, it was a four-hour drive with no major traffic issues between Vegas and L.A. A ton cheaper and you already have a car when you get there.
I live near I-15 in Rancho Cucamonga, so I usually drive to Vegas. Takes about 3-3.5 hours, allowing for a 30 min stretch/snack/restroom break in Baker....
One year I decided to fly. My nearest airport is Ontario, which is about a 15 minute drive plus
* searching and finding parking (about 10 min)
* walking through the terminal, security (20 min)
* waiting at the gate (let's say about 20 min)
* boarding the airplane (about 30 min to get everyone onboard, luggage stowed, etc)
* the actual flight, including taxi, takeoff, and landing (about 45 min)
* deboarding (about 30 min if the flight is full)
* walk to either the rental cars or the taxis (about 20 minutes, plus however long it takes to actually get a car or cab)
Total, 175 minutes, about 2.91 hours or 2 hours 54 minutes. A wash, except that I-15 traffic is much worse on Sunday or holiday Monday evenings, turning a 3-hour trip into a 5- or 6- hour trip.
That time I flew, I looked down at the crowded freeway below, and thought, "What a relief...."