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Suffice it to say that no, that's not the reason.

The reason is entirely high-card strength vs all the hands including cards less than 7, like 65, 64, etc.

EDIT: And the value of pairing the 7 vs pairing the 3, again where high card strength matters--6X pairing the 6 won't matter as often.

Given there's only two hands, they are somewhat likely to showdown unimproved, not making a pair or better. If you analyzed ten handed tables, 2-7 fares the worst.