Why?
What for?
Just because everyone else is doing it?
Leaves don't "take" energy, leaves make ALL the energy the plant needs to grow and thrive.
Less leaves = less energy being made = less potential growth.............that is how plants function!
Besides, if your plant would not need those leaves, it would not grow them in the first place!!
Also, those older leaves are a reserve of ready made plant products (sugars, carbs, enzymes, proteins etc.) that the plant will draw upon during flowering, as it is more efficient for the plant to recycle these pre-made products from its older leaves than it is to make them from new.
Remove the leaves and the plant will not have access to these reserves and will have to use energy re-making those products rather than using energy to grow flowers.
This recycling of products is the reason behind a plant going through "the fade" period.
So, as you can tell, I am very anti defoliation, the only leaves I ever remove are leaves that have gone completely yellow, for by this time, the plant has taken everything it can out of those leaves and has been able to use as much energy as possible growing flowers, rather than having to use a finite energy source making new sugars, carbs, enzymes, proteins etc., as well as trying to grow flowers.
The only time I would advocate for defoliation is when you have very large plants indoors and controlling humidity during flowering is proving impossible.