When the gamerule mobGriefing is set to true, mobs won't pick up items. That includes Villagers not picking up food, and as a result not breeding. I suggest mobs not picking up items was separated from mobGriefing and given its own gamerule.
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Thank you for your report!
We're actually already tracking this issue in MC-55218, so I resolved and linked this ticket as a duplicate.
However, that ticket has already been resolved. Depending on the resolution, that can mean that it either will be fixed in the next version, or that it is not considered a bug and won't be fixed.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
Well, if mobGriefing is set to true, then mobs as even villagers should break blocks and take them. I can't understand why active mob griefing should prevent villagers from breeding. If your mobGriefing is false, then I could understand it. But maybe it's to late for me to understand the whole bug.
But I couldn't reproduce that bug for me, either with mobGriefing true or false.
(Sorry for my bad english.)