I didn't use bait when I first started playing because of lack of cash. But since then I've become more efficient in making money and now when I start a new game, I always buy/craft bait when I get the fiberglass rod.
What I've noticed just with my eyes and not any sort of actual research is that without bait, it can take up to 30 in game minutes to get a bite. So worst case scenario is 2 bites in one hour of fishing and if one of those turns out to be trash or a fish that got away, that's a really bad hour. Best case without bait is 4 bites but that's rare. Again, without any research, I'd estimate I've had just over 2 bites an hour on average with no bait.
With bait, that practically doubles. I seem to always have a bite within 10 in-game minutes and generally 4 per hour. Add bubbles to the mix (which helps with or without bait obviously), and I get 6 hits on average every hour.
I'm sure others have done tests and calculations and there's probably tons of threads already out there if searching on Google for this info.
TLDR - bait helps and is cheap enough to be worth it. Kill every bug you see in the mines too - most take only one hit to die, even with the rusty sword. Craft your own bait with the bug meat.