I believe the whole normal spacing and intensive spacing has alot to do with how much space you have to grow and what your goals are.
If you live in the city on a small lot and dont have alot of space you may have no other choice but to grow intensively (meaning spaced closer together)
Or if you live out in the country and have plenty of room but want as much production per square foot or per acre then you could choose to grow intensively. Such as maxamizing your dollar per acre output.
I for one have plenty of space and am not that interested in dollar per acre so I can spread out more.
There are pros and cons to each system
Spacing the plants closer together keeps down the weeds and shades the soil. But it also uses more nutrients and minerals and water so you need to water more often and apply
compost or fertilizer more often.
Spacing the plants normally allows more weeds to grow (unless you mulch good) it allows the roots and plant to spread out more getting bigger and uses less water, minerals, and compost, and fertilizers.
Either way you don't get out of working the garden.