I'm new to NLHE and trying to figure out opening bet sizes.
In a $1/$2 game (assume no ante), an unopened pot has $3 worth of blinds in it. "Raising to 3BB" (i.e., the default at Pokerstars) in this case would be a raise to $6, effectively giving a caller 1.5:1 pot odds (risk $6 for a chance to win $9).
Similarly, raising by the pot would make a $3 pot into a $6 call. Again, 1.5:1 pot odds.
Why is the common parlance to approach the bet as a bet sized by the BB rather than by the pot?
I find it especially confusing, since Raising to 3BB in a pot that has limpers call the blinds make for a very silly bet size (in terms of odds, a raise to 3BB after a limber called the blinds makes a caller pay $6 for a chance to win $11, or ~2:1 rather than 1.5:1). However, raising by the pot size keeps the odds similar to an unopened 3BB raise.
Can somebody unconfuse me please?