Once daily means just that, you only have one flight that leaves from your hub to that city every day.
Yes, I know what you mean, but as I said, the exact situation makes a huge difference in whether it's "worth it" to fly them or not.
If you've got to fly 3000 miles out with an A310 to pick up 150 people, then, no, it's not. You'll spend way too much money flying way out there and operating that plane on just that single route to ever hope to make any money.
If you've got to fly 500 miles out to pick up 300 people with a A300 and you can do that 4 more times throughout the day at 4 other cities, each of which you fly to once, then, yes, it'll be worth it. It'll be worth a ton of money.
If you've got to fly that same 500 miles out but you're operating routes of only 50 people and you use, say, an F28 and you do that to 100 different destinations with a fleet of 25 planes then it may or may not be worth it depending on what you're trying to do with your CI. With that many destinations, if you keep your CI low you can absolutely make a ton of cash that way. But if you want a CI of 80 you'll spend WAY too much for the marketing costs for operating that many routes that the route won't yield enough to cover the increased CI marketing costs you get as a result of flying it.
And a whole lot of other variations.
So the answer of whether it's "worth it" to fly a route once per day is "it depends".