To keep doing something, it first has to be easy to do. And it has to work well, too. Zone 2 training satisfies both.
Zone 2 training means running for a long time at an intensity where you can still hold a conversation. In my case, I try to fill a full hour. Some people measure the intensity by heart rate, but heart rate shifts depending on whether you've had caffeine that day or how you're feeling, so it seems hard to use as a benchmark. In any case, I take an intensity I could repeat tomorrow as a reasonable zone 2.
The biggest reason people can't exercise consistently is probably that the process hurts. But zone 2 training is, by definition, an intensity you could also do tomorrow, so it's easy to sustain. And because the intensity is low, the risk of injury is lower as well.
It gives your body just the right amount of energy, which makes it a good fit for a morning routine. I started doing zone 2 runs every morning during my month-long stay in Bali.
The signature effect of zone 2 training is an increase in the number of mitochondria. That helps with endurance. The number of mitochondria is determined by exercise volume, and because zone 2 is low intensity, you can keep going for a long time and accumulate that much more volume.
Aerobic exercise is also very important for a knowledge worker's physical upkeep, so it's worth maintaining consistently.