Perennial crops are also ridiculously underused in overall food supply chains. They are more difficult to monetize in existing commodity forms because their overall system value is not captured numerically.

I think it probably has something to do with this:

(Source for the drawing: my ass)

As plants reach maturity, there's less additional biomass accumulated year after year. At least that's how i imagine it, based on animal growth. Like for cattle that's true. They grow and after 6 months i think they already have like 50% of the weight of a grown-up animal? And if you let them grow for 10 years, they would only have twice the weight than after 6 months but you pay 20x the cost to keep them alive so it doesn't pay off at all (20x the cost for 2x the yield means only 10% of efficiency). That's why they're slaughtered early. I suspect a similar reason applies to plants and why they are eaten early.

Edit: i looked up the numbers for cow and calf (child cow) weights (here and here):

• At birth: 30 kg
• After 2 months: 100 kg
• After 6 months: 200 kg
• After 12 months: 400 kg
• Mature: 600 kg