Youtube is a business not a charity. It's owned by the biggest ad server on the planet. Google.
You need to show them your goals are aligned to theirs - fantastic viewer experience and profit maximization.
I highly doubt they will send significant traffic to a channel that's not monetized, what's their incentive?
I think that's the main reason to monetize. Plus what everyone else said. But in corporate America, the greatest incentive is profit maximization. We are just tiny clogs in a giant ad machine. Go with the flow. It's easier.