Reading through comments it appears the idea is that you’re attempting to control whether or not omega matches the number with your choice of strategy, rather than what you get from matched or unmatched lotteries. So the idea seems to be that always taking onebox yields lower payoffs from matching lotteries but causes lotteries to match less often, which is beneficial because unmatching lotteries have better payoffs than matching lotteries.
EDIT:
Reading through comments it appears the idea is that you’re attempting to control whether or not omega matches the number with your choice of strategy, rather than what you get from matched or unmatched lotteries. So the idea seems to be that always taking onebox yields lower payoffs from matching lotteries but causes lotteries to match less often, which is beneficial because unmatching lotteries have better payoffs than matching lotteries.