In the early 1920s Winchester and Remington UMC produced 110gr jacketed hollow point cartridges for the .30-30. Prior to that, there were 110gr lead bullet cartridges available for small game use.
To say that the 30-30 was 'made for' 150 and 170 grain bullets, and it's not a good idea to reduce loads is to ignore over a century of use.
Historically, many could not afford more than one rifle and used the one they did own for all types of hunting. To use a 150 grain bullet at 2200 fps is a bit of overkill when shooting at small game.
The 30-30 can be, and has successfully been used for many different bullet weights at a wide range of velocity.