This is an observation. Years ago 6/5 was found only on single deck games. As a general rule the looser rules that gave less edge to the house came with higher minimum tables and 6 deck shoes. Double deck tables in general had a higher house edge with less liberal rules. An example is doubling after split, some casinos allowed it on the six deck games but not on the double deck games. The Wizard of Odds website is a wonderful source of information.
Personally I quit searching out single deck games that continued to pay 3/2 because of the tighter rules on the other options. There is a lot of discussion about 6/5 vs 3/2. You don't hear much discussion about the other rules that gives the house a added advantage. I don't play a lot of blackjack anymore. My game of choice is Ultimate Texas hold em.
