Roughing in drains in 2x4 wall

This seems like a dumb question, but:

For hanging sinks and such, I'm used to seeing 2-by blocking. But with "2x4s" now often running as skinny as 3 1/4, there is no easy way to fit both 1 1/2 PVC fittings and 2 x blocking into a wall. My inclination is to use something like 1" plywood on cleats, but wondering .....

am

Been using 3/4in. plywood for many years; you have to do what you have to do.

blocking

Where are you buying 3 1/4" 2x4's? Is that company cutting corners on other things also. I would find a different supplier. If you are referring to anchoring the water lines there are many "better" ways than wood blocking to secure them.