Its even greater where I live for some people. My daughter was able to get a young person's tickets last year for unlimited bus travel within the county (not sure whether it was all bus companies, or just the biggest) for £80/month whereas individual fares were more quite a lot than that each just into town and back on weekdays.
I don't think Kelly is asking for the price advantages of paying monthly.... I think they're asking why are bus companies so hot and bothered about not selling paper monthly tickets when they don't apparently object to selling paper daily tickets?
Over here in Europa you get bombarded with the monthly/yearly subscription. And for companies it makes much more sense, regarding cashflow/projection etc.
A single ticket has to be printed and used in the space of a few hours. A monthly pass can be printed at any time and sold until the beginning of the month, for a much higher price. Much more risky for the transportation company.
Say you have a fancy printer and can print fake monthly passes. You can print a hundred fakes today "dated" November 23, valid for December 2026, and sell them until the end of November to people who can use them in December.
Ie. the end of the month November, not the end of December. I suppose you could also sell the remainder at a discount in December.