That's your choice. You have the choice of cutoff date under Tree Settings for each tree you put up.
Later update:
Looking further, I see the description for that choice says the max date is 1930. But the max date may be changed and this description may not have been. Did you try to put 1940 in the box to see what happens?
PS To counter your argument, a possible reason to not use 1940 these days is because 1) people are living longer and 2) the risk of identity theft, as well as the impact of identity theft has greatly increased in the past few years. A few thousand dollars stolen out of a person's bank account hurts just as bad when you are 87 as when you are 67.
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