Depletion is a lot tougher and more rare than it seems. In studies they usually fully withhold CHO for a period of 12-48hrs and have participants engage in complete exhaustive exercise.
Most recreational athletes will have a hard time becoming completely depleted without really withholding CHO from their diet. Most exercise sessions simply aren't that depleting. If you look at substrate oxidation rates at different percentages of vo2 max, you could go out and do a 3hr ride at 70% of FTP with an hour of threshold intervals and even after 2100kj of work its likely that not even half of that is glycogen. If you're full when you start with ~2000kcal of glycogen stored, you still have 1000kcal left. Replenishing the 1000 you burned within 24hrs is fairly easy as that is only 250 of CHO. I'd then argue that most people train low rather than depleted.
Complete depletion is a shitty physical state. For a few months when I was lifting I used a depletion diet to cut bodyfat and on Saturday morning, after a week on less than 70g of CHO/day, I would go in and do a nearly 1.5hr continuous depletion workout. It was the worst, most horrible experience and the only reprieve was that 90min after I got to start a 24hr carb binge. It also killed my strength and energy. I can't imagine wanting to do something like this with endurance exercise. Hell, when I asked some WT riders what they thought about fasted training their response was (every once in a while, but always with some protein during the ride).
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Froome.GramzFailed Custom Bike