AA's policy is an easy business decision.
If they give PLT to LTGold w/ 25K/year then PLT's that fly 50K/year (who are larger revenue generators) will get less upgrades. Same argument for LT-PLT/EXP.
I am surprised that AA offers the Lifetime perks; I am happy they do this as I will be LT-Gold this year and LT-PLT in 3 or 4 years.