They cut the hero sleep time in half, because they nerfed them, which was followed by an outcry, for the very thing you are suggesting there was no pressure.
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Most welcome adjustment by SuperCell too.
I could have been happy with 60 minute original +2 every level. SuperCell went one better with 30 minute original +2 every level.
As for this idea, given it is ruled out and not really that game changing how about leave it be?
You can request troops every 20 minutes, it's not that big of a deal.
Heroes however, slept for up to 3 hours when it was applied to them. Big difference.