Why are hot dogs sold in packs of 10 and buns in packs of 8? It’s just the way it worked out. With hots dog buns, the pans were 4 buns per pan, but that’s arbitrary. It easily could have been 5. But it wasn’t.
With rent, landlords don’t really need the money very frequently, and collecting more often probably doesn’t provide more advantage. Whereas wages, a person has to buy food and other things, not just rent. So a longer schedule was problematic.
But that doesn’t mean a different schedule couldn’t have evolved. Weekly pay? Biweekly rent? It probably could have happened. But it didn’t. Sometimes in history, things happen arbitrarily, not for profound reasons. I can see some logic why wages would be on a shorter schedule than rent as mentioned above, but the exact timeframes…probably arbitrary.