Apparently we move in different circles.
I must be in one of those "Small and middle companies may be less common to embrace this,...". We're a shop where the policy is one company computer per employee, unless you're doing development work and need a separate test environment. (Because of our products, we can't always virtualize that.)
I find it these to be contradictory statements:
"Laptops have a longer lifecycle than desktop machines. Employees are willing to exist with a laptop longer than with a desktop at all levels."
and
"There is simply a prestige factor, as well. Executives *want* the shiniest new gadgets..."
If they're buying new gadgets, they're almost certainly replacing useful devices early.