It seems to me in your example "so that" is a form of rationalization or persuasion. "You may wear it, but you don't have to."
"For ... to" is more of a command or a direct instruction such as "You will wear this sweater because I bought it for you."
Let's try a different example:
Jodi made coffee so that she would stay awake.
Jodi made coffee for herself to stay awake.
Here, The first example is a rationalization. "There are many ways to stay awake, but Jodi chose to make coffee.
The second example is a direct instruction. "The way for Jodi to stay awake is to drink coffee."
Semantics? The explanation above regarding emphasis makes sense.